The USSR is expelled from the League of Nations because of the Soviet invasion of Finland

An assassin sent by Stalin kills the exiled Trotsky in his home in Mexico City

The Treaty of Moscow ends the war between the USSR and Finland, after 200,000 Soviet deaths in the three months of hostilities

More than 4000 Polish officers are massacred at Katyń on Stalin's orders

Adolf Hitler orders preparations to be made for Operation Barbarossa, his planned invasion of the Soviet Union

German armies cross the border to invade Russia on a front from the Baltic to southern Poland

The systematic shooting of Russian Jews by German Einsatzgruppen is the first step in the development of the Holocaust

Less than four weeks after crossing the Russian border, a German army is within 200 miles of Moscow

The first of the Arctic convoys leaves Scapa Flow, in the north of Scotland, taking Hurricane fighters and raw materials to the Soviet Union

A week or two after reaching Leningrad a Germany army establishes a siege that will last 900 days

The German advance is held just short of Moscow as winter arrives

Dmitry Shostakovich's Seventh Symphony, mainly written during the siege of Leningrad, has its premiere in Kuybishev

A renewed German campaign eastwards in Russia results in the capture of Sebastopol and the Crimea

Russia's new heavy industry is relocated to the east to escape the German advance

A desperate battle begins for the city of Stalingrad, with house-to-house fighting between Germans and Russians

Soviet tanks complete the encirclement of 20 German divisions at Stalingrad

With much of the German Sixth Army destroyed, the survivors led by Field Marshal Friedrich Paulus surrender at Stalingrad

Hitler's attempt to take Kursk (in response to Stalingrad) results in the German loss of 70,000 men and 1500 tanks

The German siege of Leningrad is finally broken, after 900 days

After relieving Leningrad, the Russians begin to drive the Germans back on all fronts

Hungary signs an armistice with the USSR

Alexander Solzhenitsyn is sentenced to eight years in a Soviet labour camp for critizing Stalin in a private correspondence

Igor Stravinsky's Symphony in Three Movements, premiered in New York, derives from music written for or inspired by films

Roosevelt, Stalin and Churchill meet at Yalta to discuss Allied post-war plans

Stalin agrees at Yalta to declare war on Japan after the end of the European war