Trotsky hurries back to Russia from exile in the United States

German U-boats sink 430 Allied and neutral merchant ships in this month alone

Canadian troops take Vimy Ridge, subsequently the site of Canada's most important war memorial

The Allies frustrate the German U-boats by introducing the convoy system

A Russian summer offensive against the Germans results in massive loss of life and territory

An armed uprising in Petrograd disperses after Lenin declines to give support

Trotsky is imprisoned and Lenin flees to Finland as Russia's Provisional Government cracks down on the Bolsheviks

Prince Lvov steps down as head of the Provisional Government in Russia and is replaced by Alexander Kerensky

Haig sends British troops over the top in the third battle of Ypres

Kerensky dismisses Kornilov as commander-in-chief, antagonizing the right wing in Russia

Russian opinion polarizes, with support growing for left-wing Bolsheviks and right-wing Kadets

Trotsky, released from prison, stages a coup to win Bolshevik control of the Petrograd Soviet

Lenin, in disguise, returns from Finland to Petrograd, where he hides in the flat of a party worker

Lenin persuades the Bolshevik central committee to vote for an armed insurrection

The dancer Mata Hari is executed in France as a German spy

Ocxtober 24 - a victory at Caporetto enables the Austrian army to penetrate far into northeast Italy

The soldiers of the Petrograd garrison mutiny on being ordered to the front

The Peter and Paul fortress is taken, giving the Bolsheviks control of Petrograd

Bolsheviks storm the Winter Palace in Petrograd and arrest the ministers of the Provisional Government

Lenin issues a Decree of Peace, inviting Russia's enemies to enter into immediate peace negotiations

Lenin's Decree on Land abolishes private ownership of large estates and promises the land to the peasants

The Bolsheviks attempt to stifle opposition in the run-up to the election for Russia's new Constituent Assembly

Suitable ground is selected by the British at the battle of Cambrai for the first serious deployment of their new tanks

The Cheka (origin of the KGB) is established to suppress political dissent in Russia

Finland wins freedom from Russia and becomes an independent republic