December 1: Gasoline rationing begins in the United States.

December 2: Manhattan Project: Below the bleachers of Stagg Field at the University of Chicago, a team led by Enrico Fermi initiates the first self-sustaining nuclear chain reaction (a coded message, "The Italian navigator has landed in the new world" is then sent to U.S. President Franklin D. Roosevelt).

December 4: In Warsaw, two women, Zofia Kossak and Wanda Filipowicz, risk their lives by setting up the Council for the Assistance of the Jews. - USAAF bombers make their first raid on Italy.

December 7: British commandos conduct Operation Frankton, a raid on shipping in Bordeaux harbour.

December 17: The Allies issue the Joint Declaration by Members of the United Nations, the first time they publicly acknowledge the Holocaust.

December 22: An avalanche in Aliquippa, Pennsylvania kills 26, including Vulcan Crucible Steel Co heir-apparent Samuel A. Stafford Sr., when two 100 ton boulders fall on a bus filled with wartime steel workers on their way home. - An airplane carrying prominent Ustashe general Jure Francetic' crashes. Francetic' dies as result of the injuries on December 27.

December 24: French Admiral Darlan, the former Vichy leader who had switched over to the Allies following the Torch landings, is assassinated in Algiers.

December 27: The Union of Pioneers of Yugoslavia is founded. (source: Wikipedia)