Richard Holmes follows the route taken between August and December 1914 by the 100,000 men of the British Expeditionary Force as they went to fight the Germans in France.

On April 22nd, the troops holding the Front were confronted with the first use of poison gas as a weapon of war. By the middle of 1915 over half of the 25,000 troops had been killed or badly wounded. Lord Kitchener's recruiting drive 'Your country needs you' prompted millions of young men to enlist. Veteran Robbie Burns, now 104, and Dick Trafford, now 102 recall the moment that they joined up. Dick also recalls the Battle of Loos where the British lost 8,000 men in an hour and Holmes relates the story of Rudyard Kipling's only son John who was among the reserves at Loos.

A visit to Verdun in France, scene of the first battle where artillery totally dominated the battlefield, leaving one million soldiers killed or wounded.

The story of the ill-fated Nivelle offensive of 1917, in which French commander Robert Nivelle galvanized 750,000 troops in a lightning attack on the German defences, only for the heavy losses inflicted on the French to lead to mutiny in the ranks. Meanwhile, the British found themselves under pressure at the third battle of Ypres, also known as Passchendaele, where the atrocious weather turned the battleground into a muddy hell. Richard Holmes also looks at the underground warfare waged during the battle.

In 1917 America joined the war against Germany, And Germany moved to finish the war quickly to their advantage. This program examines Kaiserlacht (the Imperial Battle), the massive offensive launched by the German Army on 21st March 1918. It looks at how close Germany came to winning the war at this point, and the Allied counter-offensive that eventually led to victory and the German surrender.