Born in Hamburg, Thälmann was a Social Democratic Party member from 1903. Between 1904 and 1913 he worked as a stoker on a freighter. He was discharged early from his military service as he was seen as a political agitator. In January 1915, on the day before his call-up for military service in World War I, he married Rosa Koch. Towards the end of 1917 he became a member of the Independent Socialist Party of Germany (USPD). On the day of the German Revolution, 9 November 1918, he wrote in his diary on the Western Front, "...did a bunk from the Front with 4 comrades at 2 o'clock."