The first months of World War II went very badly for the Americans. The Japanese had caught the Pacific Fleet in Pearl Harbor flatfooted and at anchor and had put a massive blow on American naval power. 

After that, the Japanese had made lightning assaults and had easily taken the Philippines, Wake Island, Guam, Thailand, Malaya, Singapore, the Dutch East Indies, New Britain, the Gilbert Islands, Rabaul, Hong Kong. They were moving to Burma, New Guinea, and reaching deeper into China. It was victory after victory and the Japanese Empire seemed unstoppable. But it all began to change. 

Admiral Isoroku Yamamoto, the architect of Pearl Harbor and the head of the Japanese Fleet, made a statement that turned out to be quite prophetic.

“In the first six months of a war with the United States, I will run wild and win victory upon victory. But then, if the war continues after that, I make no such guarantees.”