When war broke out in the Pacific, the Japanese naval air force had the world's most advanced Nakajima B5N2 torpedo-bomber aircraft, which was far superior to the American Douglas TBD-1 Devastator and a generation ahead of the British Fairey Swordfish biplanes. The Japanese aircraft were faster, more maneuverable, and could drop torpedoes from a higher altitude. After a successful debut over Pearl Harbor, these machines were involved in every major naval battle until 1944, making a permanent mark on aviation history. It was not until 1943/1944 that this superb aircraft began to be replaced by the modern Nakajima B6N Tenzan. The road to the creation of B5N was not easy and was fraught with many failures.