Mitsubishi G4M Betty
The twin-engine G4M Betty was the Japanese Navy’s mainland-based bomber of WWII, and Japan’s most produced bomber of the conflict. Test flown in 1939 and entering service in 1941, The Betty’s main assets were speed and exceptional long-range – it was designed to fly 2300 miles with a bomb load, and could do 3500 miles without. That made it difficult to intercept when used as a medium or high altitude bomber.
However, as with the Zero fighter, speed and range were bought by making the plane as light as possible, at the expense of basic protections such as armor plate and self-sealing fuel tanks. As a result, Bettys readily caught on fire when their fuel tanks were hit, earning them nicknames such as the “flying Zippo” or “type one lighter” by both friend and foe. But if it did not flame up, it was otherwise quite resilient, capable of surviving significant damage.
In addition to level bombing, Bettys were used as a torpedo bomber, and it was in that role that they sank the British battleships Repulse and Prince of Wales in the war’s early days. However, the low, slow, and steady approach required for torpedo launch took away the Betty’s speed advantage and made it and its readily flammable fuel tanks vulnerable to defensive fire.
Bettys wreaked considerable havoc during the war’s first year, inaugurating the Japanese conquest of the Philippines by devastating Clark Field, America’s main airbase in the islands, on December 8, 1941; sank the Prince of Wales and Repulse off the Malayan coast two days later; and ranged the breadth and width of the Pacific, utilizing their long-range to bomb far-flung targets from Australia to the Aleutians.
Once US fighters and trained pilots began flooding into the Pacific, Betty’s vulnerability when flying without fighter protection was exposed. While speed and range made interception difficult, when Bettys were intercepted they suffered heavily. Redesigns ameliorated the vulnerabilities by introducing plate armor and self-sealing fuel tanks, at the cost of reduced speed and range, but by then Japan was well on the way to losing the war, and the improved Bettys were flying with negligible fighter cover against swarms of US fighters. By war’s end, Bettys had been reduced to suicide bombers, or as launch platforms for missiles piloted by suicide flyers.