On December 7, 1941, at around 1:30 p.m., President Franklin Roosevelt is conferring with advisor Harry Hopkins in his study when Navy Secretary Frank Knox bursts in and announces that Japan had attacked Pearl Harbor. The attack killed more than 2,400 naval and military personnel.

For weeks, a war with Japan had appeared likely since negotiations had deteriorated over the subject of Japan’s military forays into China and elsewhere in the Pacific during World War II. FDR and his advisers knew that an attack on the U.S. fleet at the Philippines was possible, but few suspected the naval base at Pearl Harbor would be a target.

In her account of Roosevelt and first lady Eleanor during the years of the Second World War, No Ordinary Time, historian Doris Kearns Goodwin recounts the scene at the White House on that tragic and pivotal day: Eleanor had just finished hosting a luncheon and walked into FDR’s study just as he received confirmation of the attack via telephone. While aides and secretaries scurried around the room, Eleanor overheard some of her husband’s conversation and knew that, in her words, “the final blow had fallen and we had been attacked.”

Although Eleanor, who knew Roosevelt best, later recalled her husband’s demeanor on that day as “deadly calm,” she knew that he was incensed by the attacks. He was concerned that it might only be a matter of time until Germany, too, would officially declare war on the United States and that, at that moment, U.S. forces would be hard-pressed to fight a war on two fronts. According to Goodwin, he told Eleanor that it would take time for the United States to build up its military and that he feared the nation would “have to take a good many defeats before we can have a victory.” Indeed, FDR and his advisors had discussed the possibility that the Japanese were already planning an invasion of the mainland somewhere on the West Coast.

As the day wore on, Roosevelt displayed a calm and steady efficiency: He consulted with military advisors, enlisted his son James’ help to work with the media and spoke by telephone with British Prime Minister Winston Churchill, who told him “we are all in the same boat now.” Early that evening, Roosevelt dictated a speech to his secretary, Grace Tully, which he planned to deliver to Congress the next day. (Eleanor actually addressed the nation on the subject of war before her husband. That evening she delivered a scheduled weekly radio broadcast in which she told listeners that although the United States had been thrust reluctantly into the war she was confident that “whatever is asked of [America] we shall accomplish it; we are the free and unconquerable people of the U.S.A.”)

Late that night, Roosevelt updated his cabinet and Congressional members on the situation: “This is probably the most serious crisis any Cabinet has confronted since the Civil War.” One cabinet member later noted that the president was visibly distraught while recounting what he had been told of the strafing of sailors and the destruction of most of the Pacific fleet. After the meeting, Roosevelt went to bed.

The next day, Roosevelt addressed Congress and the nation with a somber yet stirring speech in which he swore that America would never forget December 7, 1941, as a “date which will live in infamy.”