On the outbreak of war in 1914, Churchill joined the War Council. However, he was blamed for the failure at the Dardanelles Campaign in 1915 and was moved to the post of Chancellor of the Duchy of Lancaster. Unhappy about not having any power to influence the Government's war policy, he rejoined the British Army and commanded a battalion of the Royal Scots Fusiliers on the Western Front.

When David Lloyd George replaced Herbert Asquith as Prime Minister, he brought Churchill back into the government as Minister of Munitions and for the final year of the war, Churchill was in charge of the production of tanks, aeroplanes, guns and shells.