Bogart was a lover of the sea and enlisted in the United States Navy in the Spring of 1918. He served as a signalman aboard the SS Leviathan, a troop transport ship. The Leviathan had previously been the Vaterland, a German passenger ship which had been seized by the Americans at the outset of their entry into the conflict. During her time in service she transported over 110,000 American servicemen to Europe.
Much of Bogart’s time in the Navy was spent after the official end of hostilities ferrying soldiers back and forth between Europe and North America. Despite this however, he still managed to somehow earn his trademark scar while serving. Accounts vary as to what exactly transpired, but what is certain is that the scar on his lip would go on to become an important part of his onscreen presence. Bogart was honorably discharged in 1919.