Franklin D. Roosevelt's speech after the attack on Pearl Harbor was effective in rallying the American people to support the war effort. Roosevelt's speech was able to convey the gravity of the situation and the need for the country to unite and fight against the common enemy. He used strong and emotive language to create a sense of national purpose and a call to action. For example, he used the phrase "a date which will live in infamy" to describe the attack, which helped to galvanize the American people. Additionally, he was able to reassure the American people that they would ultimately be victorious, which helped to boost morale during a difficult time. Ultimately, Roosevelt's speech was a powerful tool in mobilizing the American people to support the war effort and was an important moment in American history.