This aerial view shows Japan’s home fleet, arrayed in battle line, on October 29, 1940, off the coast of Yokohama, Japan. During World War II, at the beginning of the Pacific War in December 1941, the Imperial Japanese Navy (IJN) was the third most powerful navy in the world, and Japan's naval air service was one of the most potent air forces in the world. During the first six months of the war, the IJN enjoyed spectacular success, inflicting heavy defeats on Allied forces while remaining undefeated in battle. The attack on Pearl Harbor crippled the battleship arm of the US Pacific Fleet, while Allied navies were devastated during Japan's conquest of Southeast Asia. Land-based IJN aircraft were also responsible for the sinkings of HMS Prince of Wales and HMS Repulse, the first time in history that capital ships were sunk by aerial attack while underway. In April 1942, the Indian Ocean raid drove the Royal Navy from South East Asia. After these successes, the Japanese concentr...