A timeline of events before, during and after the Third Battle of Ypres (Passchendaele), one of the bloodiest episodes of the First World War.

Images of Russian soldier Maria Bochkareva and British nurse Edith Cavell appear in The Great War in Portraits, an exhibition that begins next month.

Battle of Langemarck. British soldiers (said to be watching the bombardment of the enemy lines). Near Zuydcoote, 16th August 1917.

Men of the West Yorkshire Regiment sitting in a captured German pill box waiting to go into action, near the St Julien - Grafenstafel road during the Battle of Polygon Wood, 26 September - 3 October, part of the Battle of Passchendaele.

These harrowing images chronicle the 103 days of the hell the brave men lived through as they fought and in the Battle of Passchendaele.

Battle of Langemarck. British soldiers in the ruins of a church (said to be watching a bombardment of the enemy lines). Near Zuydcoote, 16th August 1917.

The Battle of Cambrai showed how to break the deadlock on the Western Front - but at a terrible cost.