• April 6 – German troops invaded Greece and Yugoslavia.
• April 13 – Japan and Russia signed a non-aggression pact.
• April 17 – Yugoslavia surrendered to the Axis and Marshall Tito began to organize guerrilla forces.
• June 22 – Germany invaded the Soviet Union.
• July 13 – England and the Soviet Union signed a mutual aid agreement.
• August 25 – British and Soviet troops occupied Iran.
• October – German forces threatened the outskirts of Moscow and Leningrad.
• November 17 – Admiral Yamamoto and elements of the Combined Fleet steamed out of Saeki Bay, Japan.
• November 29 – Governor Ford told a convention of Native American leaders in Havre that their treatment by the Federal government had been “shameful.”
• December 3 – Sen. Burton K. Wheeler leaked the top-secret “Victory Program” to a newspaper reporter.
• December 4 – The Japanese fleet changed course towards Pearl Harbor.
• December 6 – The British declared war on Finland, Hungary, and Rumania.
• December 8 – Montana Congresswoman Jeannette Rankin cast the only dissenting vote on a declaration of war.
• December 11 – Germany & Italy declared war on the U.S.
• December 12 – The sound of a train collision in Great Falls was mistaken for an air raid.
• December 13 – A Soviet offensive at Moscow caused 85,000 German casualties. British forces in North Africa attacked Germans west of Tobruk.
• Dec. 15 – President Roosevelt addressed the nation on the 150th anniversary of the signing of the Bill of Rights.
• Dec. 18 – The first Japanese detainees arrived at Fort Missoula.
