Conversation so far:
Was Adolf Hitler a soldier in World War I?
Hitler was living in Munich and voluntarily enlisted in the Bavarian Army.
What year did Adolf Hitler enlist?
1914
Was Adolf Hitler a war hero?
He was decorated for bravery, receiving the Iron Cross, Second Class, in 1914, the Iron Cross, First Class August 4, 1918, and the Black Wound Badge May 18, 1918.
Why did Adolf Hitler get the Iron Cross?
He was present at the First Battle of Ypres, the Battle of the Somme, the Battle of Arras, and the Battle of Passchendaele, and was wounded at the Somme.

Question: How long was he in the war?
Self-contained rewrite: How long was Adolf Hitler in the war?