The Lethal Ambush That Sent 100,000 Tons of Japanese Steel to the Ocean Floor

In March 1943, Japanese naval forces faced one of the most destructive ambushes of the Pacific War. The devastating attack resulted in the loss of thousands of troops and the destruction of vital supply ships. Allied forces struck with precision, using a coordinated assault that crippled Japanese ambitions in the region.

Early Warnings and Rising Tensions

By 1943, Japan was expanding its reach across the Pacific. Their fleet was attempting to reinforce positions in New Guinea by transporting thousands of troops and supplies toward Port Moresby. Allied Coastwatchers had been tracking Japanese movements, relaying valuable intelligence that helped plot a strategy for interception.

On March 1, a U.S. B-24 Liberator patrol spotted the Japanese convoy heading for Lae and Salamaua. The convoy consisted of 16 ships, including troop transports and eight destroyers. Bad weather forced the reconnaissance team to return to base without confirming the convoy’s precise location. Determined to find the fleet, new search missions were launched the following day. Eventually, the convoy was rediscovered, providing the Allies with the chance to strike.

The Opening Attack

The Allies planned a coordinated assault. To weaken Japan’s air support, Royal Australian Air Force bombers attacked Lae airfield at dawn, damaging runways and grounding reinforcement planes. With Japanese air support diminished, U.S. B-17 bombers targeted the convoy from high altitude, releasing demolition bombs. One of the first victims was the Kyokusei Maru, a transport ship carrying troops and supplies. Explosions ripped through the ship, forcing survivors into the ocean as the vessel sank.

Japanese destroyers scrambled to rescue survivors while Allied bombers continued their assault. Ships weaved through the water, evading further strikes as darkness fell. Despite the confusion, Japanese vessels managed to maintain some distance from the attackers.

Continuous Pressure from Allied Forces

As night set in, Allied Catalina flying boats from RAAF No. 11 Squadron began tracking the convoy. The aircraft monitored Japanese movements, ensuring no escape. The convoy seemed to be slipping past the Allied net, but a Beaufort bomber from No. 100 Squadron launched a torpedo strike as the convoy moved through the Vitiaz Strait. The attack missed its mark, allowing the convoy to press on.

By morning, the Allies launched a powerful three-wave strike. Thirteen B-17 Flying Fortresses bombed from high altitude, causing severe damage to several vessels. Japanese sailors scrambled to regroup, but before they could recover, 13 Australian Beaufighters from No. 30 Squadron swept in. Flying low, they fired their powerful 20-millimeter cannons directly into the ships. The attack silenced Japanese anti-aircraft gunners and tore through ship bridges, leaving crews defenseless.

The final wave followed closely behind. Thirteen B-25 Mitchell bombers unleashed a devastating “skip bombing” attack, where bombs bounced across the water before striking ship hulls. The explosions ignited fuel stores, and several vessels burst into flames. More bombers joined the assault, ensuring no ship remained unscathed.

Aftermath of the Attack

As surviving Japanese ships scattered, PT boats from the U.S. Navy arrived to finish the job. Among the remaining vessels was the Oigawa Maru, which was quickly targeted by PT-143 and PT-150. Torpedoes struck the already-damaged ship, sending it beneath the waves.

The ambush resulted in the destruction of all eight troop transports and four destroyers. Nearly 3,000 Japanese troops and sailors perished, and the convoy’s cargo was lost to the ocean. The loss dealt a severe blow to Japanese control in the Pacific. With supplies and manpower diminished, Japanese expansion efforts in New Guinea were severely weakened.

This devastating attack became known as the Battle of the Bismarck Sea, remembered as one of the most effective and destructive Allied air assaults of the war.