Operation Starvation was an aerial mining operation conducted by the US Army Air Forces (USAAF) in WWII to disrupt shipping around the Japanese home islands. This mining proved to be the most efficient means of destroying Japanese shipping during the war. In terms of damage per unit of cost, it surpassed the USAAF strategic bombing and the US Navy submarine campaigns. |
In early July 1944, Dr. Ellis Adolph Johnson, a US Navy Commander mine warfare expert working under Admiral Chester Nimitz, officially drafted the initial mining proposal. He briefed the leadership of the USAAF XXI Bomber Command in Hawaii regarding the strategy. |
US submarines had already devastated Japan’s merchant fleet, but they could not safely navigate the shallow, tightly defended internal choke points like the Shimonoseki Strait. The US Navy possessed the mines and the intelligence but lacked long range aircraft capable of carrying the heavy mines. The USAAF’s B-29 heavy bombers were the perfect “delivery trucks” for a naval blockade. |
The US Navy supplied the advanced sea mines, along with the Naval mine warfare specialists. |
The mines laid during Operation Starvation did not detect ships using radar, nor did they require a ship to physically hit them (contact mines). They were mines with influence fuses (target‑fired triggers) that used passive sensors to detect a ship’s presence: |
- Magnetic: Triggered by the disruption or distortion a steel-hulled ship caused to the Earth’s natural magnetic field as it passed overhead.
- Pressure: Triggered by the hydro-dynamic pressure drop created under a heavy vessel moving through the water.
- Acoustic: Triggered by hydrophones that picked up the specific underwater sound frequencies of a ship’s propeller and engine vibrations.
US Navy Mark 25 Aerial Mine |
Fuses: Magnetic, Mark 25 Mod 1 had A-5 acoustic trigger. |
Length: 87.2-93 inches (221.5-236 cm)
Diameter: 22.4 inches (56.9 cm) |
Weight: 1950-2000 lbs. (885-907 kg)
Explosive charge: 1274 lbs. (578 kg) of Torpex (high explosive) |
US Navy Mark 26 Aerial Mine |
The Mark 26 was a scaled down version of the Mark 25 in the 1000-poumd class. The Mark 26 allowed a wider variety of tactical aircraft to carry it and permitted the B-29s to carry mines per sortie. |
Length:
With parachute pack: 68.5 inches (174 cm)
Without parachute pack: 64.5 inches (163.8 cm) |
Diameter:
Main Case: 18.625 inches (47.3 cm)
Tail Section: 15.75 inches (40 cm)
Parachute Pack: 18.50 inches (47 cm) |
Weight: 1000-1072 lbs. (454-486 kg)
Explosive charge: 465 lbs. (211 kg) TNT or 520 lbs. (236 kg) Torpex |
US Navy Mark 36 Aerial Mine |
The Mark 36 was an improved Mark 26 with a larger explosive charge and a slanted nose for improved underwater trajectories. |
Fuse: Acoustic, Mark 36 Mod 1 had a Magnetic fuse using a MM2 exploder. |
Diameter: 18.5 inches (47 cm)
Length: 63 inches (1.6 m) |
Weight: Total 1024-1,082 lbs. (464.5-490.8 kg)
Explosive charge: 570 lbs. (258.5 kg) TNT or 638 lbs. (289.4 kg) Torpex |
Each mine was equipped with a six-foot (182.88 cm) diameter parachute. The parachute slowed the mine’s descent to ensure a soft landing on the water and not damaging the mine’s internal mechanisms. After landing, the parachute automatically detaches from the mine and the mine sinks to rest on the sea floor (known as a “bottom mine”). |
The primary challenge of aerial mining of Japan is that the sea mines must be dropped into highly specific, narrow underwater channels to be effective. If dropped too far off-course, they could land outside the enemy shipping lanes or land safely onshore where the Japanese could recover them. |
The B-29s were equipped with the AN/APQ-13 radar system, which included the H2X (3 cm) radar (“Mickey”) and the Q‑13 range‑finding computer to precisely drop the aerial mines into narrow enemy shipping lanes. The H2X radar could “see” through cloud cover and the darkness by detecting land as bright spots and water as dark areas. These radars were also used for navigation, weather avoidance, and for collision avoidance. Sometimes the radar was used for landing on runways in foggy conditions. |
The radar’s 9.375 GHz X‑band parabolic antenna which rotated 360 degrees was mounted on the B‑29 in a radome between the two bomb bay doors on the aircraft’s belly. The first versions were partly retractable. Later versions were fixed in a more streamlined radome. |
This is a photo of a B-29 with the radome visible on the belly. In many photos, the open bomb bay doors or the main landing gear obscured it. Because it was a high security feature, censors often retouched photographs. It appears a censor had whited out the nose wheel cover. The B-29 is nicknamed “Case Ace” with an Ace of Spades playing card painted between the words. Case Ace is a term used in the five card stud poker game. |
The radar operator’s desk was custom‑fabricated and located in the rear area of the aft pressurized crew compartment. The radarscope or indicator is on the left, the Q-13 range computer in the center, and the main control box is to the right. |
The B-29s would individually fly low-altitude missions at night between 5000 and 8000 feet (1524 and 2438.4 meters). The radar would give the navigator highly detailed topographic fixes on prominent coastlines, small islands, and inland waterways. The radar would also give the bombardier exact ground speed and ranging distance relative to a shoreline landmark. By factoring in the aircraft’s speed, altitude, and wind drift, the radar indicators told the crew exactly when to pickle (release) the mines. |
The AN/APQ-13 radar system became standard factory-installed equipment on the B-29 starting in mid-1944. From late 1944 to early 1945, approximately 250 to 300 existing earlier production B-29s were retrofitted with the AN/APQ-13 radar system by field modification depots and specialized Continental Modification Centers. |
On 26 July 1944 during a high-level Pacific strategy conference in Hawaii with US President Franklin D. Roosevelt and General Douglas MacArthur, Admiral Nimitz advocated that Japan could be entirely defeated by a combination of severe blockade and bombardment, making a bloody land invasion unnecessary. |
General Henry “Hap” Arnold and the top USAAF brass were aggressively lobbying for an independent post-war US Air Force. To secure political independence from the US Army, they needed to prove that independent, strategic precision bombing could win the war alone. Mine laying was viewed as a “defensive” or “collateral” naval task that diverted precious B-29s away from their primary, headline-grabbing mission of bombing Japanese industrial cities. When forced to compromise, General Arnold limited the allocation of B-29s to just a single bombardment group to minimize the “distraction” from his strategic bombing campaign. |
To keep the B-29s out of the US Navy’s direct control, the USAAF ensured that the US XX Air Force reported directly to the Joint Chiefs of Staff in Washington, with General Arnold acting as its commander, rather than reporting to Admiral Nimitz in the Pacific theater. |
When Major General Curtis LeMay took over command of the XXI Bomber Command in January 1945, he was initially unenthusiastic about the naval mandate. He preferred high-altitude incendiary raids. However, after facing heavy pressure from Nimitz’s staff to protect the upcoming invasion of Okinawa, LeMay finally accepted the US Navy’s request. |
LeMay realized he could maximize the efficiency of the order. Instead of spreading a single bombardment group thin, LeMay assigned the entire 313th Bombardment Wing (BW) equipped with B-29s to the operation. He reasoned that a concentrated effort would finish the job faster and allow the wing to return to its main objective of bombing. |
The 313th BW consisted of 4 Bombardment Groups (BG). The tail markings for the 313th BW was a 126 inch (3.2 m) diameter black circle which outlined a 63 inch (1.6 m) high black group letter. The tail tip was painted in the Bombardment Group’s color. The engine cowling covers were often painted the Bombardment Group’s color to increase its visibility. |
Each Bombardment Group consisted of 3 Bombardment Squadrons (BS). Victor numbers were individual bomber identification numbers used for radio communications and operational scheduling. The number range determined which squadron in the bomb group the B-29 belonged to. |
In May 1944, the three bomb squadrons of the 504th BG were the 393rd, 398th, and the 421st. In November 1944, the 393rd BS was reassigned to the 509th Composite Group leaving the 504th to be a 2 bomb squadron group. During mid June 1945, the 680th BS was attached to the 504th BG which brought the group up to full strength with 3 bomb squadrons. |
The Victor numbers were located in these specific places on the B-29: |
- The Forward Nose: Painted in large text directly below or ahead of the cockpit glass.
- The Front Landing Gear Door: Stenciled in black or white text for easy identification by ground crews.
- The Rear Fuselage: Painted on both sides of the rear fuselage, aft of the national insignia.
Some B-29s did not have a Victor number in the photographs due to a lack of time for applying all the markings to newly arrived B-29s. They were usually replacement aircraft. |
On 24 July 1944, the US 2nd and 4th Marine Divisions assaulted the island of Tinian (southwest of Saipan) in the Mariana Islands. The Tinian invasion was the perfect amphibious operation of the Pacific war. It differed from most in that the proximity of Saipan, approximately 5 nautical miles (9.3 km or 5.8 miles) across the Saipan Channel, allowed it to be executed as a shore-to-shore operation instead of a ship-to-shore operation. Fire support (land based artillery) and air support was available from Saipan. On August 2nd, the island was declared secured. |
Tinian is 1500 miles (2400 km) south of the Japanese home islands which was within the 1500-mile combat radius of the B-29. A round trip bombing mission from Tinian to Japan took B-29 crews roughly 14 to 15 hours to complete. |
In mid-August 1944, the US Navy Seabees began the transformation of Tinian into a base for the B-29 bombers. Two air bases were constructed, North Field and West Field. These were on the sites of existing Japanese airfields. They had to be lengthened to 8500 feet (2600 m) and widened to 500 feet (150 m) to handle the large B-29s. Three new additional runways were built on the North Field. |
On Tinian, the Seabees had about 80 power shovels (such as Bucyrus-Erie or Northwest models) working in the coral pits loading the fractured coral into dump trucks. The trucks then hauled the coral material over dedicated “haul roads” directly to the runways. |
A Seabee Caterpillar D8 bulldozer behind a truck dumping its load of crushed coral on a runway. The D8 dozer then spreads out the piled coral. |
Road graders (right) leveled the runways and road rollers packed down the coral. On the left is a captured Japanese Sakai 10-Ton Diesel 3-Wheel Roller. |
In December 1944, the 313th BW arrived from the USA and was based at North Field. In May 1945, the 509th Composite Group arrived and moved to North Field, where it took over an area that had been specially constructed for its special missions. Two B-29s of the 393rd BS, 509th Composite Group became famous for dropping the atomic bombs on Hiroshima and Nagasaki on 6 and 9 August 1945. |
When all the construction work was completed on 5 May 1945, North Field had four parallel new runways, with 8 miles (13 km) of taxiways, 265 hardstands, 173 Quonset huts and 92 other buildings. In 1945, Tinian’s North Field was the largest and busiest airfield in the world. |
The Japanese built and used this concrete building as the air operations administration building and the airfield control tower. The 313th BW used this building for air operations and this building was used as the North Field’s control tower while the Seabees were expanding the airfield. Next to the building on the right is a Japanese Type 88 75mm Anti-Aircraft gun. Parked in front of the building is a US Jeep on the left and a motorcycle in the center. |
This is the rear of the building. This building and tower was adequate for the Japanese with only one runway for fighter aircraft. The tower was not tall enough to view over the tails of the B-29s parked along four wide runways. The tail of the B-29 stood 27 feet, 9 inches (8.46 meters) tall from the ground. |
The red square on the left panel is the location of the 313th BW air operations building. The blue square in the upper center is the location of the new taller control tower which is shown on the right panel. |
The upgraded base featured a distinct grid-like layout, with coral roads named (like “Broadway” and “42nd Street”) to match those in Manhattan Borough, New York City, USA. The four runways at North Field were lettered “A” (Able) , “B” (Baker), “C” (Charlie) and “D” (Dog) from north to south. The red square north of Runway A is the 313th BW air operations building. The blue square is the location of the new control tower. The center section of Runway A was built over the smaller Japanese airfield. |
The 6th BG B-29s were parked on the south side of Runway D, then going north the 9th BG was parked between runways C and D. The 504th BG between B and C, and the 505th BG on the northeast side of Runway A. Later, the 509th Composite Group were parked on the north side of Runway A, west of the control tower. Each B-29 was assigned to a specific hardstand so the ground crew could set up simple quarters and store spare parts for it. |
The groups used the runway to the north side of their parking area hardstands, expect for the 505th and the 509th which both used Runway A. If there was a crash or a mechanical problem and a runway was temporary closed, the B-29s in the take off queue would been diverted to one of the other runways. |
This view is looking west-southwest down the length of the runways on Tinian. North is to the right. |
The heavily laden B-29s favored taking off to the east. The Seabees constructed the eastern ends of the runways right up to the edge of an 80 foot (24.4 meters) coral cliff overhanging the Pacific Ocean. This design allowed the overloaded bombers that struggled to achieve optimal lift to literally “drive off the cliff”. Dropping slightly off the edge toward the water gave the aircraft a brief window to gather vital airspeed and achieve stable, level flight. |
To adapt their B-29s for mine laying missions, the 313th BW worked alongside the US Navy Mine Modification Unit (MMU) to implement several structural, electrical, and tactical modifications. In early April 1945, the MMU relocated to Tinian. |
Bomb Bay Structural Modifications |
The standard B-29 bomb bays were built to cradle conventional, aerodynamic GP (General Purpose) or incendiary bombs. Naval acoustic and magnetic influence mines were vastly different in shape, weight distribution, and deployment mechanisms. The internal bomb-bay racks and release shackles were modified to safely hold and drop the massive aerial mines. The structural modifications maximized the B-29’s mine payload capacity, allowing each B-29 to carry up to twelve 1000-pound mines or seven 2000-pound mines (or a customized combination of both mine types). |
A 2000-pound Mark 25 aerial mine is being loaded in the bomb bay of a B-29. |
A 1000-pound Mark 26 aerial mine in the bomb bay of a B-29 is being checked. The large cylindrical object running across the top of the bomb bay is a pressurized tunnel which connects the forward and aft crew compartments. |
Electrical and Release Upgrades |
Because the mines relied on parachutes to slow their descent and prevent the sensitive internal electronics from shattering upon ocean impact, the release system required specialized integration. The bomb bays were rewired with specific static lines and arming wire systems. When a mine was dropped, the static wire automatically deployed the tail-shuttle parachute. Technical crews calibrated the AN/APQ-13 attack radar systems to feed precise environmental data directly into the bomb-release circuitry, enabling automated “blind drops” over pitch-black or cloud covered coastal waters. |
Weight and Defensive Stripping |
Following tactics championed by General LeMay for low-altitude night operations, the B-29s underwent a dramatic weight-reduction process. To offset the immense weight of the naval mines and maximize fuel efficiency for the long flight from the Tinian to Japan, the B-29s were stripped of most of their heavy defensive gun turrets and ammunition. Only the twin .50-caliber machine guns in the tail turret were kept for basic rear defense, as the missions were flown individually at night when Japanese fighter interception was highly unlikely. |
During the low-altitude night mine laying mission, the B-29 crews bypassed traditional visual bomb-sights entirely, relying instead on a data sharing pipeline between the AN/APQ-13 radar operator, navigator, and bombardier to pinpoint the exact release window for the mines. |
Radar Mapping via the AN/APQ-13 |
Because water absorbs radar waves while land reflects them back strongly, waterways like the critical Shimonoseki Strait showed up as pitch-black channels outlined by bright, glowing shorelines on the radar scope. The Radar operators used distinct, highly identifiable land features, such as peninsulas, small islands, or sharp harbor bends as radar reference points (check points). |
Micro-Navigation and Radar Tracking |
Crews did not simply drop mines when they “saw” the target. Mine laying required incredibly narrow placement tolerances to build uniform underwater blockades without overlapping mines. The navigators calculated exact geographical target coordinates and plotted a precise approach vector using airspeed, altitude, and wind drift calculations. As the B-29 approached the target at the low altitudes, the radar operator tracked the reference land features on the scope, providing constant range and bearing corrections to the navigator. |
The Release Coordination Chain |
Because the radar scope was located at the radar operator’s station, not in front of the bombardier, the final mine release was handled through a highly coordinated, verbal crew pipeline: |
- The B-29 had to stabilize perfectly at a pre-calculated altitude, airspeed, and heading.
- The radar operator monitored the distance to the release point on the scope, feeding real-time distance adjustments to the navigator.
- The navigator closely monitored the flight instrument variables and countdown sequence. At the exact microsecond the aircraft intersected the target zone, the navigator yelled a command over the interphone, prompting the bombardier to activate an intervalometer, a timing device that automatically released the mines from the bomb bays in a rapid, spaced-out succession.
The primary tool for in-flight verification was the O-15 radar camera attached to the AN/APQ-13 radar scope. At the exact millisecond the bombardier released the mines, the camera automatically snapped a photograph of the radar screen. The photo captured the exact alignment of the aircraft relative to the shore at the moment of release. Back at the base on Tinian, intelligence officers used these photographs to cross reference the radar geometry and mathematically map out exactly where the mines fell. |
Since they were dropping mines blind, the navigator and radar operator kept meticulous logs of precise data points: The exact altitude and ground speed were noted at the point of release and the crew calculated wind vectors right before the run to determine how much the mines’ parachutes would drift during descent. |
By calculating the time elapsed from a known radar-identified landmark (like a cape or island) to the drop point, they could calculate their position to within yards (meters). If the flight math matched the flight plan, the drop was deemed a success. |
If any flight parameter deviated or the radar picture lost clarity, the crew was ordered to abort the drop to prevent the advanced influence mines from landing at an incorrect location. |
The B-29s were outfitted with 1945 cutting-edge airborne radar-jamming transmitters (such as the AN/APT-1 “Dina” and AN/APT-3 “Mandrel”). Special electronic countermeasures (ECM) operators on the B-29s tuned these transmitters to the specific frequencies of Japanese early-warning and gun-laying radars used (typically around 100 to 200 MHz). The transmitters emitted continuous radio static, completely blotting out the B-29 blips on the Japanese radar scopes. |
The B-29 crews also dropped massive quantities of chaff. Chaff was bundles of aluminum foil, cut to match the wavelengths of Japanese radars, were dispersed into the air. The falling foil created huge cloud-like echoes on Japanese radar screens, making it impossible for their radar operators to pinpoint the exact location, altitude, or speed of the B-29. The chaff launcher/ejector was located inside the unpressurized rear bomb bay, with the dispenser chute opening protruding through the left-hand side of the lower fuselage skin. |
Before flying real combat sorties over Japanese home waters, individual aircrews were required to complete four to eight localized training flights. These flights involved practicing multiple radar approaches over featureless water and culminated in dropping inert dummy mines into the ocean surrounding the island to ensure the release procedures were executed and the mechanisms functioned flawlessly. |
Overhead aerial view of three B-29s during formation flying practice at low-altitude in March 1945. |
The most iconic, widely published photographs of the campaign were photos of B-29 44-69985 named “Jake’s Jalopy” of the 9th BG, 99th BS (Circle X) with Victor number 53 dropping parachute-retarded Mark 25/26 naval mines during a day time training flight off the coast of Rota Island (northeast of Guam and southwest of Tinian) shortly before the official operation was launched. |
B-29 “Jake’s Jalopy” regular crew included: Pilot: Captain Alden D. “Jake” Jacobson, Co-Pilot 2nd Lt. Edward P. Platek, Bombardier 1st Lt. John N. Hansen, Navigator 2nd Lt. Robert H. Wilson and Radar 2nd Lt. David J. Carrigan, Engineer TSgt Allen J. Goff, Radio Sgt Jullius Feferblum, Central Fire Control Sgt Mario DeLorenzo, Left Gunner Sgt David T. Hartupee, Right Gunner Sgt George Fields and Tail Gunner Sgt Robert A. Lasto. |
B-29 “Jake’s Jalopy” had just released a Mark 26 acoustic aerial mine from the forward bomb bay during the training flight. The mine’s parachute had started to deploy. |
An overhead view of a Mark 26 mine after dropped from the B-29’s bomb bay. The mine’s parachute is fully deployed. |
Two Mark 26 mines falling from B-29 “Jake’s Jalopy”. On lower right side of the photo are four frames of a Mark 26 mine landing in the water. |
During March to June 1945, B-29 “Jake’s Jalopy” completed 29 combat missions which included standard night and day bombing raids as well as 5 mine-laying operations in May. In July 1945, B-29 “Jake’s Jalopy” reached the end of its front line combat tour and was converted into a “Super Dumbo” rescue plane. The conversion involved stripping out selective bombing mechanisms to accommodate extra emergency communications gear, survival provisions, and search equipment. |
On 9 August 1945, B-29 “Jake’s Jalopy” went on a “Super Dumbo” mission and while flying over southern Japan observed the mushroom cloud from the atomic bomb “Fat Man” dropped on Nagasaki. |
This map illustrates Japan’s shipping lanes before the start of the campaign. |
Rather than a single mission, the campaign was comprised of 46 separate combat missions split into 5 distinct operational phases. The operation is historically tracked by the specialized tactical phases and dates set by the US XX Air Force high command. |
Phase I: Support of the Okinawa Invasion (March 27th to May 2nd) |
Interdicting the Shimonoseki Strait cut off 80% of Japan’s domestic merchant traffic. It prevented the Japanese Navy from sending warships, reinforcements, or supplies to counter the Allied invasion of Okinawa (launched April 1st). The shipping routes originating from major military embarkation ports like Hiroshima and Mutsure were bottled up. |
Missions:
March 27-28: 102 B-29 sorties launched against the Shimonoseki Strait.
March 30-31: 85 B-29 sorties hitting the Shimonoseki Strait.
April 6-7: 48 B-29 sorties targeted the waters off Kure and Hiroshima.
April 12-13: 11 B-29 sorties deployed to reinforce Shimonoseki Strait. |
Phase II: Industrial Center Blockade (May 3rd to May 12th) |
Disregarded purely tactical naval targets and pivoted heavily towards a total commercial blockade. Targeted and choked off major industrial shipping nodes throughout the Inland Sea. Seeded minefields outside the major commercial ports of Tokyo, Nagoya, Kobe, and Osaka to halt the flow of raw materials and imported food. Performed critical “re-mining” of the Shimonoseki Strait to maintain closure after initial Japanese clearance efforts. |
Missions:
May 3-4: 88 B-29 sorties hit the Shimonoseki Strait and the Inland Sea.
May 5-6: 86 B-29 sorties targeting Tokyo, Nagoya, Kobe, and Osaka harbors.
May 12-13: 35 B-29 sorties strike the Shimonoseki Strait and Inland Sea. |
Phase III: Northwest Honshu & Kyushu Interdiction (May 13th to June 6th) |
Broke up alternative supply lanes by targeting the northwest ports: |
Northwest Honshu Ports: Niigata, Nanao (Toyama Bay), Tsuruga, Sakata, and Maizuru.
Kyushu Ports: Moji, Fukuoka (Hakata Port), Sasebo, Nagasaki, and Karatsu. |
Completely disrupted domestic maritime logistics sailing across the Sea of Japan. New low-frequency acoustic and pressure mines were deployed to overwhelm the Japanese mine sweeping capabilities. |
Missions:
May 13-14: 30 B-29 sorties hit Shimonoseki Strait and Kyushu lanes.
May 16-17: 25 B-29 sorties against northern Honshu shipping lanes.
May 18-19: 28 B-29 sorties targeting Miyazu, Maizuru, and Tsuruga.
May 20-21: 30 B-29 sorties distributed across various northwestern ports.
May 22-23: 33 B-29 sorties mined Fushiki and Nanao ports.
May 24-25: 31 B-29 sorties reinforcing northwestern Honshu.
May 26-27: 29 B-29 sorties striking the Shimonoseki Strait.
May 27-28: 28 B-29 sorties providing logistical cutoff across the Inland Sea. |
Phase IV: Intensified & Secondary Port Blockade (June 7th to July 8th) |
This phase introduced newer mine types (such as water pressure displacement detonators). The entirety of Japan’s major shipping lanes were blanketed with continuous, rolling single-group missions flown every second night. The blockade parameters were extended to hit secondary and tertiary ports along Honshu and Kyushu. High mine density over previously established minefields were sustained to ensure all major industrial naval traffic officially grounded to a halt. |
Missions:
June 7-8: 26 B-29 sorties mined northern Honshu ports and Fukuoka.
June 9-10: 32 B-29 sorties mined the ports of Niigata and Nanao.
June 11-12: 26 B-29 sorties hit Shimonoseki Strait and northwestern ports.
June 13-14: 30 B-29 sorties dropped onto the Shimonoseki Strait bottleneck.
June 15-16: 31 B-29 sorties sent to mine Fukuoka and Karatsu.
June 17-18: 25 B-29 sorties striking Kobe and Osaka.
June 19-20: 27 B-29 sorties reinforcing the Inland Sea choke points.
June 21-22: 28 B-29 sorties targeting the outer waters of Honshu.
June 23-24: 26 B-29 sorties deployed to target dynamic shipping channels.
June 25-26: 26 B-29 sorties focused on northwestern Honshu blockades.
June 27-28: 29 B-29 sorties targeting the strategic passages around Kyushu.
June 29-30: 31 B-29 sorties reinforcing western Honshu.
July 1-2: 27 B-29 sorties striking Shimonoseki Strait fields.
July 3-4: 30 B-29 sorties deployed across primary harbor entry points.
July 5-6: 28 B-29 sorties mining remaining unblocked harbors.
July 7-8: 29 B-29 sorties targeting shipping infrastructure. |
Note: The June 9-10 mission group was split into two groups. The second group simultaneously re-mined the Shimonoseki Strait. XX Air Force considered these two group objectives to be two distinct missions. |
Phase V: Total Blockade & Korean Extension (July 9th to August 15th) |
The remaining gaps in the blockade were sealed by flying mining missions across the Tsushima Strait to target crucial occupied Korean ports (such as Masan, Pusan, and Chongjin). The final desperate routes carrying food supplies from mainland Asia across the Sea of Japan were cut off. The total closure of peripheral industrial ports like Niigata and Moji, brought Japan’s international and domestic maritime traffic down to 5%. |
Missions:
July 9-10: 31 B-29 sorties mining the Korean ports of Pusan and Masan.
July 11-12: 29 B-29 sorties targeting Wonsan and Hungnam ports.
July 13-14: 30 B-29 sorties deployed to mine northern Honshu ports.
July 15-16: 32 B-29 sorties mining the Shimonoseki Strait and Fukuoka.
July 17-18: 30 B-29 sorties deployed to coastal Korea and the Inland Sea.
July 19-20: 31 B-29 sorties targeting remaining deep-water ports.
July 22-23: 26 B-29 sorties reinforcing the Shimonoseki Strait.
July 24-25: 28 B-29 sorties deployed to Korean ports and Najin.
July 27-28: 31 B-29 sorties dropped advanced pressure mines around Honshu.
July 29-30: 29 B-29 sorties executing a massive sweep of the Inland Sea.
August 1-2: 33 B-29 sorties deployed to seal the ports of Niigata and Nanao.
August 5-6: 27 B-29 sorties deployed to strike maritime shipping junctions.
August 7-8: 28 B-29 sorties mining dynamic harbor access fields.
August 14-15: 39 B-29 sorties completely lock down the remaining open coastlines of Honshu. |
In the mid-morning hours of August 15th, the B-29s of the last mission returned to Tinian before the Japanese announced their unconditional surrender to the Allies. |
To clear the mined areas during the US campaign, Japan relied on magnetic sweep gear designed to mimic a ship’s magnetic footprint from a safe distance. |
The primary tool used was the “L-Sweep,” consisting of long, buoyant insulated copper cables towed behind a wooden hall minesweeper. Large generators aboard the minesweeper sent powerful pulses of electricity through the cables into the water. This generated an artificial magnetic field strong enough to trick the mine’s magnetic sensors into detecting a large steel hull was passing over, causing the mine to detonate harmlessly behind the sweeping vessel. |
To defeat this Japanese countermeasure, the US Navy developed the A-6 Fuse and incorporated it in the Mark 25 Mod 2 mine. |
It combined a magnetic-pressure trigger mechanism that integrated a ship-counter. It required both the magnetic signature and the physical water-pressure drop of a ship hull to detect a ship, rendering conventional magnetic wire sweeping method useless. |
The ship-counter (also known as delayed-firing mechanisms or clickers) were sophisticated counter-countermeasure devices built into the fuses of magnetic, acoustic, and pressure influence bottom mines. Its primary function was to render an area “sweep-proof” by ignoring a preset number of ship passes (often minesweepers) before finally arming and detonating the mine later under a high-value target such as a cargo or troop ship. |
Because these mines were entirely mechanical and electrical (predating microprocessors), the ship-counter functioned through a highly ingenious combination of low-power relay systems, clockwork gears, and stepping switches. |
The mine ordnance officer manually set the mine’s ship-counter on the field before the mission. By setting a mechanical dial or selector switch, they chose the exact number of counts required, typically ranging from 1 to 15. For example, if the mine’s ship-counter is set to 10. For the first 10 ships that the mine detects, the mine’s detonator remain physically disconnected and those ships pass over the mine unharmed. After the 10th ship had passed over, the mine then becomes “armed”. The next ship that passes over the mine (the 11th ship) would trigger the sensor(s) and the explosive charge detonates. |
The Mark 25 Mod 2 mine was first deployed with on the May 3rd mining mission of Phase II and were used along with acoustic mines to the end of the campaign. |
B-29 42-24825 named “Patty Sue”, number 14 of 6th BG (Circle R), 24th BS on Tinian’s North Field. The pirate logo was painted on all the B-29s of the 6th Bomb Group. It represented the group’s pre-WWII Caribbean heritage, having spent many years serving in the Panama Canal Zone and the Caribbean area. The character depicted is the famous French-American pirate and privateer Jean Lafitte (1780 to 1823). |
This is my close up of the mission markings on B-29 “Patty Sue”. |
The three spiked balls are the universally recognized symbol for a naval mining mission. They represent mine laying missions on: |
May 20: The Shimonoseki Strait / Hamamatsu mining run.
May 22: The secondary Shimonoseki Strait approach mining run.
July 11: The historic long-range mining mission to Rashin and Pusan, Korea. |
To the left of the three mine missions is a torii gate-style marking which represent missions flown directly over the Japanese mainland. A torii is a traditional Japanese gate most commonly found at the entrance of or within a Shinto shrine. |
When large formations of B-29s took off from the Marianas (like Tinian and Guam) for daylight high-altitude, high-explosive ordnance missions, dozens of B-29s needed to find each other in the sky to assemble before heading to the target. Prominent colored bands or stripes across the tail fin were used to identify the B-29 as a “Lead” or “Formation Leader” plane. The bright and contrasting bands allowed the B-29s in the group to easily spot, track, and form up on their designated flight leader. |
B-29 44-69865 named “Tinny Ann”, number 16 of the 6th BG (Circle R), 24th BS has black and yellow stripes painted on the tail fin forward of the Circled R. The tail tip and the engine cowlings are painted red. |
B-29 44-69920 named “T.N.Teeny.II.”, number 3 of the 9th BG (Circle X), 1st BS has black and yellow stripes painted on the tail fin. On the ground under the port (left) wing appears to be a step ladder laying on its side. |
B-29 “T.N.Teeny.II.” flew a total of 29 missions while on Tinian. The top row mission markings in this photo are spiked naval mine balls with a parachute above the mine indicating 10 mine laying missions. The second row has 12 red bombs (daylight high-altitude mission) and 2 black bombs (nighttime low-altitude incendiary firebombing missions). The missing 5 missions were either completed after the photo reference was taken, or they consisted of non-combat/special profiles (such as visual reconnaissance, weather tracking, or sea-rescue search missions) which crews frequently did not log with mission markings. |
B-29 42-24791 named “The Big Time Operator”, number 4 of the 9th BG (Circle X), 1st BS flew 48 missions, which included 8 mining missions. |
This is my close up of the nose of B-29 “The Big Time Operator”. Each of the mine markings had a parachute on top of the mine. Two confirmed Japanese aircraft were shot down by the B-29’s gunners. |
The nose art of B-29 “The Big Time Operator” is Walt Disney’s Donald Duck wearing a tuxedo and top hat with radio headphones. |
B-29 44-70070 named “THE 8 BALL”, number 16 of the 9th BG (Circle X), 1st BS parked on its hardstand. On the belly the radome is visible. |
A close up of the nose of B-29 “THE 8 BALL”. The top row is 11 mine laying missions and the second row has 19 bombing missions. |
A B-29 of the 505Th BG (Circled W) is on it hardstand next to damaged ex-Japanese buildings north of Runway A somewhere on the east end. |
This is my close up of the starboard (right) engines and the tail section of the B-29 in the above photo. For some unknown reason, there is a white star painted on a color square on the outer side of the B-29’s number 4 engine. It is also assumed that there was a white star on the B-29’s number 1 engine. |
This is my close up of the vehicle next to the building in the above photo. It is a Dodge WC-62 or a WC-63 (with a power winch mounted on the front bumper) 6×6 weapons carrier. The nose of the B-29 appears to have some nose art but a name is not legible. |
This is a line B-29s of the 505th BG (Circle W). This specific photograph was taken from the elevated vantage point of the Tinian control tower looking eastward over the hardstand parking apron. At least two B-29’s have black/yellow lead stripes on the tail fin. On the right, B-29 number 42 can be seen. |
Taking off from Tinian’s North Field was highly risky due to severe aircraft overloading, unreliable and overheating engines, and unforgiving runway geography that left no margin for error. |
Because the round-trip combat missions to Japan covered nearly 3000 miles (4828 km), each B-29 had to be heavily overloaded with fuel, ammunition, and up to 20000 pounds (9071.85 kg) of bombs or sea mines. A fully laden B-29 could weigh up to 65 tons (58967 kg), which pushed the aircraft to its absolute aerodynamic limits and required the whole length of the runway just to reach stall speed. |
If a B-29 suffered an engine failure or mechanical issue past the halfway mark of the runway, the heavy plane could not slow down in time. It would overrun the tarmac and slide down the abrasive coral cliff. |
B-29A 42-93894 named “Lassy Too”, number 41 of the 505th BG (Circle W), 484th BS on Tinian’s North Field in early June 1945. |
B-29A “Lassy Too” was one of 27 B-29s that were to mine four harbors in Japan on the night of June 22-23, but crashed on takeoff due to an engine failure. All of the crewmen survived, and the other 26 B-29s completed the mission. Here the crashed B-29 is being recovered from the end of Runway A the next morning. Note the fuel tanker truck by the nose of the B-29. |
This is another view of the crashed B-29A “Lassy Too”. In front are two Autocar Model U-7144-T 4-to-5 ton 4×4 tractors towing fuel semi-trailers. B-29A “Lassy Too” was carrying a full mine load and the fuel tanks were full. The fuses were removed from the mines and the fuel tanks were emptied before the written off B-29 was removed. In the background is a Biederman P-1 crane and a Diamond T truck. |
Some unlucky B-29s not able to become airborne on takeoff or ran out of fuel on the return flight ended up ditching in the sea. Upon hitting the water, the tail of this B-29 broke off and sank. The B-29’s nose section is under water. A surviving crewman is clinging to the Number 1 engine at the top. |
B-29 44-69846 named “The Spirit of F.D.R.”, number 4 of 504th BG (Circle E), 398th BS was very lucky. |
On July 3rd during a night-bombing mission over Himej, Japan, B-29 44-69846 suffered a midair collision with another B-29. One of the other B-29’s props tore through the tail, completely destroying the rudder. The crewmen elected to stay with the crippled B-29, first heading out to sea to be rescued by a submarine, then headed toward Iwo Jima, and lastly, back to Tinian. B-29 44-69846 landed safely on Tinian and was eventually repaired with a new rudder. |
Each bomb symbol on this map represents 10 aerial mines dropped. |
| Phase | Date Ranges (1945) | Number of Missions | B-29 Sorties | B-29 Losses | Mines Laid |
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| I | March 27 to May 2 | 4 | 246 | 5 | 2112 | | II | May 3 to May 12 | 3 | 209 | 0 | 1422 | | III | May 13 to June 6 | 8 | 234 | 3 | 1313 | | IV | June 7 to July 8 | 17 | 452 | 1 | 3542 | | V | July 9 to August 15 | 14 | 424 | 6 | 3746 | | Totals ==> | 141 Days | 46 | 1565 | 15 | 12135 |
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Minor operational variations in primary vs. secondary field diversion accounts can adjust exact sortie totals by 1 or 2 B-29s per night depending on the historical resource consulted, but the cumulative total equals approximately 1529 successful operational sorties out of 1565 total flown by the 313th Bomb Wing. |
The mines were laid in 26 different mine fields. 103 US airmen were lost and over 670 Japanese ships were sunk or severely damaged. |
During the whole campaign, only 15 B-29s were lost to all causes, an attrition rate of less than one percent. 11 out of 15 were: |
B-29 44-69675 named “The Bad Penny” of the 6th BG, 40th BS, crashed in Shimonoseki Strait due to engine failure on 27 March 1945. MACR 13464. All 11 crewmen were KIA. |
B-29 42-24916 named “The Peacemaker”, number 54 of the 6th BG, 40th BS, lost from unknown cause over the Shimonoseki Strait while on mission to sow mines on 27 March 1945. MACR 13465. All 11 crewmen bailed out and became POWs. |
B-29 42-24864 named “The Stork Club Boys” of the 504th BG, 398th BS, lost from unknown cause on 27 March 1945 while on mission to sow mines over the Shimonoseki Strait near Yawata, Japan. MACR 13462. 8 crewmen were KIA, 2 bailed out and became POWs. |
B-29A 42-93911 named “Trigger Mortis”, number 28 of the 6th BG, 39th BS, was hit by AAA fire over the Shimonoseki Strait while on mine sowing mission on 27 March 1945. Able to return to base. All the crewmen survived. The aircraft was repaired, but retired from combat with 22 missions, and was transferred to the 358th Air Service Group (Supply Line Management) on Tinian. The plane was scrapped in 1950. |
B-29 42-65283 named “The Big Wheel” of the 9th BG, 99th BS, crashed on Tinian on 30 March 1945 due to mechanical failure while on a mission to sow mines in the Shimonoseki Strait. After the mechanical failure, the mines were jettisoned and the plane headed back to Tinian. 10 crewmen were KIA, 1 survived. Aircraft was destroyed. |
B-29 42-63509 named “Long Winded” of the 9th BG, 99th BS, was shot down by AAA fire over the Shimonoseki Strait while on mine-sowing mission on 22 May 1945. 7 crewmen were KIA, 3 survived and were rescued by US Navy submarine. |
B-29 42-93894 named “Lassy Too”, number 41 of 505th BG, 484th BS, crashed on takeoff at North Field, Tinian on 22 June 1945 due to engine failure. All the crewmen survived, but the aircraft was destroyed. |
B-29A 42-93939 nicknamed the “Little Giant” of the 6th BG, 40th BS, was lost during a night mining mission to the Shimonoseki Strait on 9 July 1945. Reports from other B-29s on the mission stated that one B-29 in the formation was caught in a number of searchlights, sustained several direct flak hits and was seen to spiral down and crashed in flames. The 40th BS was the only squadron in the area and only B-29 “Little Giant” did not return. The commander of the 40th BS, Lieutenant Colonel Elmer Austin Dixon, was aboard as an observer. Dixon was declared KIA on 10 July 1945. |
B-29 44-70116 named “Sharon Linn”, number 3 of the 6th BG, 24th BS, was shot down by AAA fire and crashed at the bend of the Agano River in an area known as Yakeyama, Japan on 20 July 1945 while on mission to mine Niigata Harbor. All 11 crewmen bailed out and became POWs. Four crewmen were hanged by angry Japanese civilians. |
B-29 42-24918 number 58 of the 504th BG, 680th BS, was hit by AAA fire over the Shimonoseki Strait on 27 July 1945 and ditched 50 miles (80.5 km) south of Shikoku, Japan. MACR 14796. 5 crewmen were KIA, 6 were rescued by US Navy submarine USS Whale SS-239. |
B-29A 42-94041 named “Umbriago II”, number 46 of the 504th BG, 680th BS, was hit by AAA fire while on a mining mission over the Shimonoseki Strait on 27-28 July 1945 and crashed in Inland Sea. MACR 14797. 5 crewmen were KIA, 6 bailed out and were rescued by US Navy aircraft (Consolidated PBY Catalina or Martin PBM Mariner flying boat). |
The crew originally flew 14 combat missions in B-29 42-24913 named “Thunderin’ Loretta”, number 13 of the 9th BG, 1st BS. On 19 March 1945, it was damaged in flight due to a structural failure caused by flying directly into the violent, super heated updrafts created by the incendiary firestorms over Japanese cities. |
On the night mission of May 27-28, the crew was flying in replacement B-29 44-69811 named “Tinny Anne”, number 7 of the 9th BG, 1st BS. |
Their mission was to lay mines in the harbors of Moji and Karatsu Bay, Japan. Over the target area they were hit by AAA fire and was observed by another B-29 spiraling out of control with the left outboard engine on fire, no parachutes were observed. B-29 “Tinny Anne” became a fireball and crashed into Moji-Oosato Okuda in Kitakyushu. |
Of the 11 crew members, 10, including the pilot, Captain Stanley C. Black, were KIA. Bodies were found in the wreckage of the aircraft, as well as the bodies of those who died when their parachutes failed to open. People who gathered at the crash site peered into the wreckage and poked around the aircraft remains. Soon, members of the Moji Military Police detachment arrived, and the bodies of the US Airmen were buried in the cedar forest of Okuda, on the slopes of Mt. Kazashi, and behind the Awashima Shrine. In June 1946, the remains of the crewmen were recovered by a US Quartermaster Graves Registration Platoon. |
Kōsaiji Temple is located in Moji Ward, Kitakyushu City. |
Because the head priest of this temple mourned the US Airmen at the site of the B-29 crash, there is a memorial monument for the crew of the downed B-29 on the temple grounds, which can be seen in the lower left of this photo. Branches of a Japanese maple tree is hanging over it beside the steps. |
The Japanese text 追悼碑 at the top translates to “Memorial Monument” or “Cenotaph” in English. The name “PALMER, Chales S. 25” (Charles is mis-spelled) inscribed on the lower left of the memorial monument was a sergeant and the tail gunner on the B-29. He was the only survivor of the B-29 crew, and although he parachuted out, he was captured and taken prisoner. |
Sergeant Charles S. Palmer was sent to the Kyushu Western Military District Headquarters in Fukuoka. He died after undergoing medical experimentation in Fukuoka on 2 June 1945. He is memorialized with the missing at the Honolulu Memorial in Honolulu, Hawaii. |
After the announcement of the Japanese unconditional surrender on 15 August 1945, it took the US Navy 13 days to clear the initial paths and anchorages into Tokyo Bay. On 27 August 1945, the Auk-class minesweeper USS Revenge (AM-110) met with the destroyer USS Ellyson to take aboard a Japanese harbor pilot who provided maps of the local mine fields and underwater defenses of the bay. At approximately 0630 hours on August 28th, the USS Revenge led a small vanguard of US Navy minesweepers, including the Token, Tumult, and Pochard, north through the Uraga Channel (Uraga Suido) which is the waterway connecting Tokyo Bay to the Sagami Gulf. |
By the afternoon of August 28th, the minesweepers had successfully swept a wide channel and charted safe anchorages. This allowed the very first column of the Allied occupation fleet (led by the destroyer USS Southerland and the cruiser USS San Diego) to safely enter and drop anchor in Tokyo Bay by 1314 hours. Five days later, the historic formal surrender ceremony took place aboard the battleship USS Missouri on September 2nd. |
International law required the belligerent country who seeded the mines to clear them. Since the US military had planted these mines, they were responsible for their removal. After Japan surrendered, the US Navy conducted as a series of coordinated geographic clearance operations under the broader US Pacific Fleet Post-War Mine Sweeping Plan, which utilized individual operation code names for different regional sectors. |
Operation Skagway was a massive primary operation tasked with clearing mines in the East China Sea, the Ryukyu Islands (Okinawa), and the southern approaches to Japan. |
Operation Juneau focused specifically on clearing the dense minefields in the Yellow Sea and the waters surrounding the Korean Peninsula to guarantee safe passage for occupation ships. |
Due to the sheer number of mines deployed and the high risks involved, the US Navy simply did not have enough minesweepers to execute the sweeps alone. Beside the US mines, the Japanese also laid their own mines around their harbors to counter the expected Allied invasion of the home islands. To clear the waters quickly, the Allied General Headquarters (GHQ) mandated a joint effort: |
US Navy Mine Squadrons spearheaded the initial sweeps using wooden-hulled and the fleet minesweepers. |
The Japanese government was ordered to establish a dedicated bureau, the Japanese Mine Sweeping Bureau. It composed of roughly 10000 former Imperial Navy sailors and 350+ remaining Japanese vessels. With US Navy oversight, the Japanese ships sweep their harbors for mines. |
This massive post-war effort proved incredibly dangerous. |
On 29 December 1945, USS Minivet (AM‑371), an Auk‑class minesweeper, struck a mine in the Tsushima Straits while sweeping for mines, sank rapidly, and lost 31 crewmen out of its 100 officers and enlisted sailors. It was the first US Navy minesweeper sunk during the dangerous post‑WWII mine sweeping operations. |
The US mines were equipped with a sterilization feature that rendered them harmless after a set period of time. To verify this, the US Navy sent modified ships into the minefields to detonate the mines under controlled conditions. |
The US Navy used specially modified ships as “guinea pig” vessels to test and detonate sea mines in Japanese harbors and waterways. The US Navy’s “Guinea Pig Squadron” consisted of three sacrificial ships: |
- USS Marathon (APA-200), a Gilliam-class attack troop transport ship that served as the flagship of the squadron.
- SS Pratt Victory, a standard Victory-class cargo ship transferred to the US Navy from the War Shipping Administration.
- SS Joseph Holt, a mass-produced Liberty-class cargo ship, also acquired from the War Shipping Administration.
The ship’s boilers and engines were entirely operated via remote control from the main deck and flying bridge. This ensured no crewmen would be trapped below the waterline in the hull if a mine tore open the bottom of the ship. The decks and bulkheads of the ships were heavily padded to protect the crew. To absorb the violent upward kinetic energy of an underwater blast, the crewmen stood on mattresses or floating wooden gratings rather than the steel decks. |
Each ship was manned by a minimal crew of just 22 volunteers who wore US Army tanker helmets to protect their heads from mine blasts.
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The three sacrificial ships typically steamed in an staggered echelon formation about 150 yards (137.16 meters) apart. A fleet tugboat packed with emergency salvage and rescue gear trailed exactly 1500 yards (1371.6 meters) behind them to patch up damaged hulls or rescue survivors if a ship began to sink. |
It took nearly a year just to open the primary shipping lanes. The US Navy officially retired from full-scale sweeping operations around Japan in May 1946, leaving the remaining mine fields to the Japanese units. The Japanese continued mapping and clearing mine fields well into the 1950s. |
Operation Starvation was a staggering success, choking off 35 of Japan’s 47 vital convoy routes around the main islands and sinking over 1.25 million tons of shipping. By August 1945, the Japanese people were on the verge of starvation. Food, oil, petroleum and raw materials from China and Korea were cut off. Japan’s main source of food, fishing, was paralyzed due to their fishing boats were without fuel. The Japanese Navy pressed fishing trawlers into service as minesweepers and sub-chasers, |
Japan’s rice Harvest suffered because the farmers lacked chemical fertilizers, fuel, and equipment. Military conscription of young rural men left fields with inadequate labor to tend and harvest the rice. |
Many factory workers began to not go to work for days. They were out wandering the countryside forging for food for their family. Many non-damaged factories were shutdown due to a lack of fuel, electricity, or required materials. |
The US Strategic Bombing Survey concluded that Operation Starvation was arguably the most cost-effective campaign in the Pacific. Many analysts noted that if the USAAF had ignored its rivalry with the Navy and agreed to the Navy’s mining request a year earlier, Japan might have been starved into unconditional surrender without the need for a land invasion and there probably would been no need for the Atomic Bomb. |
A Mark 25 aerial mine is on display in the WWII Gallery at the National Museum of the United States Air Force in Dayton, Ohio. |
On 14 December 2023, the Japanese Maritime Self-Defense Force (MSDF) discovered and safely cleared an active US WWII aerial mine in the Kanmon Straits. The dangerous weapon had been hidden until it was discovered during the underwater survey work for an offshore wind farm project. Also found in the same area was 19 shells and bombs believed to have been discarded by the Imperial Japanese Navy. |
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