World war II timeline - December 1940

1 December 1940	Italian submarine Argo torpedoes Royal Canadian Navy destroyer Saguenay, killing 21, but not sinking the ship. Saguenay had been escorting an eastbound convoy 300 miles west of Ireland.
7 December 1940	German cruiser Admiral Hipper breaks into the North Atlantic through the Denmark Straits. In Egypt, Lieutenant General Sir Richard O'Connor leads the Western Desert Force from Mersa Matruh with 30,000 troops and 275 tanks, to attack Italian positions at Sidi Barrani.
8 December 1940	In Egypt, British troops pass through a gap in a chain of Italian defensive camps near Sidi Barrani, preparing to attack from the rear the following day.
9 December 1940	In Egypt, British forces launch Operation Compass, attacking Italians at the Nibeiwa camp, quickly overtaking the position. In Egypt, British forces attack Italians at the Tummar East and Tummar West camps.
10 December 1940	At Sidi Barrani, Egypt, the Indian 4th Division with two tank regiments from British 7th Armored Division capture thousands of Italian soldiers. Wilhelm Keitel issues a brief order stating that Operation Felix, the capture of Gibraltar, would not be carried out at this time, as Spanish leader Francisco Franco refused to allow a German invasion of Spain. Adolf Hitler issues Directive No. 19: "Undertaking Attila", detailing plans to occupy more of France if French forces in colonies show signs of revolt. Preparations are to be made to prevent the French fleet sailing to British hands, and to take control of French airports. Adolf Hitler orders German air units to Southern Italy, to attack British ships in the Mediterranean.
11 December 1940	Near Sidi Barrani, Egypt, a reserve brigade of British 7th Armored Division captures 14,000 retreating Italian troops.
13 December 1940	Adolf Hitler issues Directive No. 20: "Undertaking Marita", to prevent the English establishment of an air base in the Balkans, which would threaten Italy and Romania. To achieve this, the forces in Romania must be increased, to be moved across Bulgaria to the north coast of Aegean when weather permits.
15 December 1940	British forces drive Italians out of Egypt, and invade Libya. The British Royal Air Force accidentally bombs the railroad station in Basil, Switzerland. Japanese Admiral Isoroku Yamamoto reveals Operation Z to his Chief of Staff, an attack on Pearl Harbor, Hawaii.
16 December 1940	134 British bombers attack Mannheim, Germany. 476 buildings are damaged or destroyed. This is the largest aerial raid on a single target so far in the war. It is also the first reprisal raid, approved by the War Cabinet, for German attacks on British towns.
17 December 1940	British Prime Minister Winston Churchill instructs a British delegation of military officers who will meet with American counterparts in Washington that they not request American protection of Singapore, Australia, or India. Only minimum force should be used against Japan, with all efforts directed toward the defeat of Germany.
18 December 1940	Adolf Hitler issues Directive No. 21 "Case Barbarossa". German Armed Forces are to be prepared to crush Soviet Russia in a rapid campaign. The final objective is to erect a barrier against Asiatic Russia on a line of Volga to Archangel. Rumania and Finland will give active support on the flanks of the German attack. The operation is named for the conquering 12th century Teutonic Emperor Frederick Barbarossa.
25 December 1940	The Soviet Attaché in Berlin passes on to Moscow Hitler's Directive 21 of December 18, the operational order for Barbarossa.
29 December 1940	American President Franklin Roosevelt gives a national radio address, suggesting that the US become "the arsenal of democracy".