December 7, 1941 was, famously, “a date which will live in infamy.” President Franklin Delano Roosevelt proclaimed it so at a Joint Session of Congress the following day, referring to the Japanese attack on the U.S. Naval Base at Pearl Harbor. Through official records, diary entries, and conversation transcriptions, we can piece together what the president was doing on the day that would bring the United States into WWII.
Tensions had been running high between the U.S. and Japan for at least a decade prior to the attacks. Upset by Japanese military expansion into China throughout the 1930s, the United States froze Japanese assets at home and refused to sell oil to the empire, actions that went into effect in July 1941.
Thanks to U.S cryptanalysts who cracked Japanese diplomatic code, American officials learned of Japanese troop buildup in November 1941. Roosevelt even sent a memo on December 1, one week prior to the attacks on Pearl Harbor, asking for more intel on the Japanese government's intentions, writing that “these increased forces in Indo-China would seem to imply the utilization of these forces by Japan for purposes of further aggression.” [PDF]
On December 7, Japanese planes began air strikes on Pearl Harbor at 7:48 AM Hawaiian time, which was 12:48 PM in Washington, DC. According to his stenographer’s diary, Roosevelt was meeting with Chinese Ambassador Dr. Hu Shih at the White House then. Immediately after this meeting, FDR had lunch in the Oval Study with aide Harry L. Hopkins. During this lunch, at 1:40 PM ET, Roosevelt took a telephone call from the Secretary of the Navy, who alerted him that Pearl Harbor was under attack (and that it was definitely “no drill”).
The subsequent meetings held by and for the president can be seen in this copy of his stenographer’s diary, via the Franklin D. Roosevelt Presidential Library:
At 6:40 PM ET, FDR spoke on the phone with Treasury Secretary Henry Morgenthau, Jr., who had their conversation transcribed [PDF]. During their talk, Morgenthau, who was in control of the Secret Service, said, “We are not going to let any Japanese leave the country or to carry on any communications,” to which the president replied, “I see.” Morgenthau also requested to put a “detail of soldiers on the White House grounds,” a suggestion at which Roosevelt balked. “You’ve doubled the guard,” he said, “That’s all you need. As long as you have one about every hundred feet around the fence, it’s all right.”
During his emergency cabinet meeting at 9:45 PM ET, Roosevelt presented, in broad strokes, what he was going to say to Congress the next day. A confrontation occurred when Secretary of State Cordell Hull disagreed with FDR’s plan to deliver such a brief speech. According to a diary entry from Agriculture Secretary Claude R. Wickard, Hull had said that “the most important war in 500 years deserved more than a short statement.” FDR ignored Hull, and he gave his heralded, barely seven-minute “Infamy” speech the next day anyway: