USS Arizona (BB-39) burning after the Japanese attack. A Nakajima B5N level bomber dropped a Type 99 Number 80 Mark 5 1,760 pound (800 kilogram) modified 16-inch (406 mm) naval shell that penetrated near Arizona's Number Two turret and caused the forward ammunition magazine to explode. The projectile was rated to penetrate 5.9 inches (150 mm) of armor plate. The exact sequence of the explosion has never been determined; Arizona burned for days. The identity of the bombardier that struck Arizona remains in dispute. Gordon Prange, in At Dawn We Slept, credited IJN Soryu aircrew flying B5N "BI-318": Warrant Officer Haruo Sato (pilot), Petty Officer First Class Noboru Kanai (bombardier) and Petty Officer Second Class Yoshikazu Hanada (radio). This crew were killed over Wake Island two weeks after Pearl Harbor. Kanai's diary, published after At Dawn We Slept went to press, indicated he attacked USS West Virginia (BB-48) and USS Tennessee (BB-43). Hiryu's B5N level bomber flight group, commanded by Lieutenant Commander Tadashi Kusumi, were officially credited with the destruction of USS Arizona. However, Kusumi was a pilot, not a bombardier, so he would not have ordered the bomb drop. Regardless of which Japanese pilot destroyed Arizona, the Type 99 Number 80 Mark 5 had a number of misfires, and an unexploded bomb was recovered from USS West Virginia (BB-48). The bomb was rarely used in combat again.