Yamamoto Isoroku changed American history with his idea for the attack of Pearl Harbor. Without his ideas for the attack, and without his months of careful planning, the attack on Pearl Harbor would never have been possible, and The United States may not have entered WW II. He was a very knowledgeable man. To many people, Yamamoto is believed to be one of the most influential men who is not American in our nations great history. The United States at that time were trying to maintain isolationism, because they wanted to stay out of world affairs. They would have continued so, if it wasn't for Isoroku's plan. To think that one man, one Japanese man, was able to push the United States into entering the war, is unreal to put into perspective. To prove how smart he was, the quote below is one of his own, which supported his belief that a prolonged war with the U.S would lead to a Japanese defeat.