The day after Japan’s attack on Pearl Harbor, President Roosevelt went to the House of Representatives to deliver his “Day of Infamy” address and ask the House for a formal war resolution. The measure was passed with just a single nay from a principled pacifist. Undaunted, Italy’s leader Benito Mussolini took the opportunity to reinforce his message that the “Powers of the Pact of Steel” would prevail, and following his speech Chancellor Adolf Hitler at the Reichstag in Berlin, Germany, announced what everyone knew was coming.

On this day, December 11, in 1941, Adolf Hitler announced that following the mutual-defense agreement with Japan, Germany was declaring war against the United States.

In practical terms, the exchange of declarations changed little. The entire length of the Atlantic separated Germany and Italy from the United States. For the moment it could only continue to provide military aid to Britain, as it had been doing – and which was one of the reasons leading up to Hitler’s decision to declare war. President Roosevelt meanwhile pushed hard for action. “The forces endeavouring to enslave the entire world now are moving towards this hemisphere,” he said in a speech. “Delay invites danger. Rapid and united efforts by all peoples of the world who are determined to remain free will ensure world victory for the forces of justice and righteousness over the forces of savagery and barbarism.”