The WWII Plane with 18 Machine Guns That Was Never Meant to Be a Gunship

Early Struggles in the Pacific

In the first months of the Pacific war, American bomber crews discovered the limits of their equipment and training. The North American B-25 Mitchell had been designed as a medium bomber, but when enemy fighters broke through thin escort screens, survival depended on something the aircraft did not yet have—overwhelming defensive firepower.

In 1942, newly built B-25s were rushed to Australia and into combat with little preparation. Standard bombing runs at 10,000 to 12,000 feet proved disastrous. At those altitudes, Japanese flak batteries and Zero fighters could strike effectively. Escort fighters such as the P-40 and P-39 lacked the range to follow deep into enemy territory. This left B-25s alone for the most dangerous part of their missions, resulting in frequent losses before bombs could even be released.

Shifting to Low-Level Raids

Crews, frustrated by attrition, began ignoring official altitude rules and flew at treetop level. This improved bombing accuracy and helped evade some heavy flak, but it exposed them to small arms and light anti-aircraft fire. In one April 1942 raid over New Guinea, six of eighteen bombers were lost, a loss rate that commanders knew was unsustainable.

When General George Kenny took over the Fifth Air Force in mid-1942, he realized standard doctrine would not work. He approved experimental ideas, including a radical proposal from Major Paul “Pappy” Gunn. Instead of relying only on bombs, Gunn suggested filling the aircraft’s nose with heavy machine guns, effectively turning the bomber into a gunship.

The Improvised Gunship

Gunn’s crews worked with limited tools, cutting aluminum by hand and riveting panels together in open-air workshops. They added up to eight .50 caliber Browning machine guns in the nose, along with more in waist, dorsal, and tail positions. The changes shifted the bomber’s weight dangerously forward, requiring adjustments and test flights that always carried the risk of structural failure.

In March 1943, the modified B-25s faced their first major test during the Battle of the Bismarck Sea. Flying as low as 200 feet over the water, they combined strafing fire with a new tactic called skip bombing, where bombs were released to bounce across the surface before striking ships. The machine guns cleared decks of enemy gunners, allowing the bombs to hit with devastating results. In that battle, eight troop transports and four destroyers were sunk, halting a major reinforcement attempt.

From Field Modifications to Factory Models

The success at Bismarck Sea convinced both the U.S. Army Air Forces and North American Aviation to formally adopt the gunship idea. By late 1943, the B-25G rolled out of factories with a solid nose housing a 75mm cannon alongside multiple machine guns. Later, the B-25H added even more forward-firing weapons, with some versions carrying up to eight in the nose alone.

The cannon-armed versions were powerful but difficult to use. Each shot produced violent recoil that rattled the airframe, shook rivets loose, and blinded pilots with smoke. Reloading was slow and demanding, as navigators had to lift heavy shells into the breech under combat conditions. Against fast-moving targets, machine guns proved more effective, offering sustained fire instead of single heavy blows.

A Flying Wall of Fire

By 1944, crews pushed the concept even further. Some field-modified Mitchells carried as many as 14 forward-firing .50 caliber guns, with extreme versions mounting 18. These aircraft flew at treetop height or just above the waterline, attacking ships, supply depots, and airfields with walls of fire that rivaled entire squadrons of fighters.

The risks were enormous. At such low altitudes, even small bursts of flak could cripple the bomber. Engine hits were often fatal since there was no room to recover or bail out. The extra guns made the aircraft heavier and less agile, but the destructive power they delivered proved decisive in many Pacific operations.

By the end of the war, the B-25 had evolved from a vulnerable medium bomber into a heavily armed aircraft that redefined what a bomber could do. It was never meant to be a gunship, yet field improvisation and necessity transformed it into one of the most formidable aircraft of World War II.