<P> The consequences were world - changing . Prime Minister Winston Churchill knew that the survival of the British Empire depended on American aid, and since 1940 had frequently asked Roosevelt to declare war . Churchill aide John Colville stated that the prime minister and American Ambassador John Gilbert Winant, who also supported the British, "sort of danced around the room together" as the United States would now enter the war, making a British victory likely . Churchill later wrote, "Being saturated and satiated with emotion and sensation, I went to bed and slept the sleep of the saved and thankful ." By opening the Pacific War, which ended in the unconditional surrender of Japan, it broke the power of an Asian check on Soviet expansion . The Allied victory in this war and subsequent U.S. emergence as a dominant world power, eclipsing Britain, have shaped international politics ever since . </P> <P> Pearl Harbor is generally regarded as an extraordinary event in American history, remembered as the first time since the War of 1812 that America was attacked in strength on its territory by another country--with only the September 11 attacks almost 60 years later being of a similarly catastrophic scale . It was the first decisive defeat for the United States in World War II . It has become synonymous with "surprise attack" ever since in American parlance . The U.S. mistakes of intelligence collection, sharing, and analysis leading to the Japanese success at Pearl Harbor did not, in the end, lead to lessons learned . </P> <P> Some Japanese today feel they were compelled to fight because of threats to their national interests and an embargo imposed by the United States, the United Kingdom and the Netherlands . The most important embargo was on oil on which its Navy and much of the economy was dependent . For example, Japan Times, an English - language newspaper owned by one of the major news organizations in Japan (Asahi Shimbun), ran numerous columns in the early 2000s echoing Kurusu's comments in reference to the Pearl Harbor attack . </P> <P> In putting the Pearl Harbor attack into context, Japanese writers repeatedly contrast the thousands of U.S. non-combatants killed there with the hundreds of thousands of Japanese civilians killed in U.S. air attacks on Japan later in the war, even without mentioning the 1945 atomic bombings of Hiroshima and Nagasaki by the United States . </P>

When did us attack japan after pearl harbor