The Japanese attack on Pearl Harbor on December 7, 1941 - "a date which will live in infamy," President Franklin Delano Roosevelt said at the time - was a defining moment in American and world history that led to the outbreak of World War II.

Japan effectively declared war on the United States on that day, in a move that many Americans - then and now - considered unprovoked. But Japan considered the attack inevitable for a number of political and economic reasons, making the conflict more complicated than generally acknowledged.

Images from Life.com commemorating the anniversary include a proposed draft of Roosevelt's "infamous" speech, scenes from Pearl Harbor on the day itself and America's reaction in the days to follow.