Foreign ministers of Germany, Italy, and Japan signed the Tripartite Pact in Berlin, pledging mutual military assistance and recognizing each nation's dominance in its respective sphere of Europe and Asia. The pact aimed to deter the United States from entering the war but instead accelerated the alignment of America with Britain and the Soviet Union against the Axis powers.
By September 1940, Germany had conquered much of Western Europe, Italy sought an empire in the Mediterranean and Africa, and Japan pressed its expansion into China and Southeast Asia. The three powers formalized their alliance in a ceremony at the Reich Chancellery in Berlin, with German Foreign Minister Joachim von Ribbentrop, Italian Foreign Minister Galeazzo Ciano, and Japanese Ambassador Saburō Kurusu signing the document.
The pact's central clause promised mutual assistance if any signatory were attacked by a power not already involved in the European war or the Sino-Japanese conflict—a provision aimed squarely at deterring the United States.
Instead, the pact hardened American resolve. It confirmed suspicions of a coordinated global fascist threat and pushed Washington toward greater support for Britain and, eventually, direct war against all three Axis powers after Pearl Harbor. The alliance was more symbolic than operational; Germany, Italy, and Japan rarely coordinated strategy and fought largely separate wars.