Final answer:
President Franklin D. Roosevelt repeated 'last night Japan attacked ...' to emphasize the severity and urgency of the Japanese attacks, alert the public to the crisis, and create a memorable soundbite that would unite the nation for war.
Step-by-step explanation:
Why FDR Repeated the Phrase 'Last Night Japan Attacked ...', President Franklin D. Roosevelt repeated the phrase 'last night Japan attacked ...' to emphasize the severity of the attack and to make it clear that the Japanese military carried out a wide-ranging and coordinated surprise attack on multiple American territories in the Pacific.
The repetition served as a rhetorical device to hammer home the extent and deliberate nature of the Japanese offensive, thus underscoring the urgent need for a U.S. response.
By emphasizing that these attacks occurred 'last night,' Roosevelt also provided a sense of immediacy and ongoing crisis, alerting the public to the fact that the situation was current and pressing, requiring immediate action by the United States.
Furthermore, the particular construction of the phrase contributed to creating a memorable soundbite that would resonate with the public and the media, reinforcing the gravity of the events and the necessity for war. In doing so, Roosevelt used the speech as a form of wartime rhetoric designed to unite and mobilize the American public for the war effort.