The purpose of roosevelt's speech is mostly to

boost morale among americans and reassure them that the military will take action against japan
persuade congress that going to war with the japanese is necessary
engage the audience by providing examples of the violence of the attack
persuade congress and the american people that becoming involved in the war is a bad idea in spite of the attacks on pearl harbor

Boost morale among Americans and reassure them that the military will take action against Japan.

Explanation:

In 1941, while Pearl Habor's base was in ruins, US President Franklin Roosevelt came to a declaration of war against Japan. In his speech, he said: "yesterday, December 7, 1941, a the date that will live in infamy, the United States has been deliberately attacked by the naval and air forces of the Empire of Japan. No matter how long it takes to overcome this premeditated invasion, the American people in their just power will win to absolute victory. "

Roosevelt hoped that this speech could boost morale among Americans and assure them that the military will take action against Japan.

After a 10-minute speech, Roosevelt was applauded, and that afternoon the declaration of war was signed. The US president wore a black belt on his arm to symbolize mourning for the lost lives in Pearl Harbor. After that, US defense groups were mobilized on both coasts of the country.

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