Cheyenne's Pal (1917)

During World War I, westerner Cheyenne Harry is a horse seller, but he refuses to part with his favorite horse and friend, Cactus. One night, broke and drunk, he sells Cactus to an Englishman for $350 which he soon loses gambling. When Harry discovers that Cactus is being sent to the war in France and probable death, he gets a horse- tending job on the ship. When they get the opportunity Harry jumps off the ship with Cactus and they swim to shore. Harry is eventually caught but is allowed to work off his debt and keep Cactus.

Unfortunately the movie Cheyenne's Pal is not yet available on HBO Max.