| 17 Feb | British destroyer HMS Cossack board the german Altmark in Norway and free 400 british prisoners. |
| 21 Feb | Soviet Union bombs Pajala, Sweden. |
| 13 Mar | Finland signs peace treaty with Soviet Union |
| 18 Mar | Italy joins the war with Germany. |
| 8 Apr | British and french ships mine norwegian coastal waters and ports. |
| 9 Apr | Germany invades Denmark and Norway (Operation Weserübung). |
| 14 Apr | The allies send forces to Norway. |
| 3 May | Vidkun Quisling becomes leader in Norway and King Haakon leaves Norway. |
| 10 May | Germany invades Belgium, Luxembourg, Holland and France. |
| 10 May | British Prime Minister Neville Chamberlain resigns and is replaced by Winston Churchill. |
| 10 May | British forces land on Iceland. |
| 11 May | Belgian fortress Eben Emael captured by german troops. |
| 13 May | Dutch Queen Wilhelmina leaves the Netherlands. |
| 14 May | Germany bombs Rotterdam. |
| 15 May | Holland surrenders. |
| 19 May | Britain bombs Bremen and Hamburg. |
| 20 May | German forces reach the English Channel. |
| 26 May | Evacuation of Allied troops from Dunkerque begins (Operation Dynamo). |
| 27 May | Belgium surrenders. |
| 8 June | Allied forces are evacuated from Narvik, Norway. |
| 8 June | British carrier HMS Glorious sunk. |
| 10 June | Norway surrenders. |
| 10 June | Italy declares war on Britain and France. |
| 10 June | Italy invades France and bombs Malta. |
| 11 June | Britain bombs Turin. |
| 14 June | Germans occupy Paris. |
| 18 June | Soviet Union invades the Baltic States (Estonia, Latvia and Lithuania). |
| 18 June |
Germany begins transporting troops through neutral Sweden with the permission of the swedish government. |
| 22 June | France signs an armistice with Germany. |
| 24 June | France signs an armistice with Italy. |
| 27 June | Soviet Union invades Romania. Romania cedes Bessarabia and northern Bucovina to the Soviet Union. |
| 28 June | Britain recognizes General Charles de Gaulle as the Free French leader. |
| 30 June | Germany invades the Channel Islands. |
| 3 July | French fleet in Oran, Algeria, sunk by the british fleet. |
| 9 July | Vichy is made the capital of France. |
| 10 July | Battle of Britain begins. |
| 11 July | Philippe Pétain is made leader of Vichy France. |
| 19 July | Adolf Hitler brodcasts peace offer to Britain, but it is rejected. |
| 3 Aug | Italy invades British Somaliland. |
| 8 Aug | German Luftwaffe begin bombing the british radar-installations. |
| 19 Aug | Italy controls entire British Somaliland. |
| 25 Aug | Britain bombs Berlin. |
| 3 Sep | USA trades Britain 50 destroyers for Atlantic bases. |
| 13 Sep | Italy invades Egypt. |
| 16 Sep | USA introduces conscription. |
| 23 Sep | The allies attack Dakar. |
| 27 Sep | Tripartite Pact (Axis) signed by Germany, Italy and Japan. |
| 7 Oct | German troops enter Romania. |
| 23 Oct |
Adolf Hitler meets with the spanish dicator Franco to persude him to join the war, but fails. |
| 28 Oct | Italy invades Greece from italian occupied Albania. |
| 1 Nov | Italy bombs Athens and Salonika. |
| 14 Nov | Greek army repels the italian invasion and enter Albania. |
| 20 Nov |
Hungary, led by Miklos Horthy, joins the axis powers. |
| 23 Nov |
Romania, led by Marshall Ion Antonescu, joins the axis powers. |
| 23 Nov |
Slovakia, led by Premier Tuka, joins the axis powers. |
| 15 Dec | British troops begins an offensive in North Africa. |