Captain Zahl is a former Nazi U-boat captain who battled from time to time with the Doom Patrol. As a U-boat captain, Zahl was ruthless and effective, and achieved the highest kill rate of any other commander in the German fleet. After the Nazis were defeated by the allies, Captain Zahl worked as a mercenary for years, until a run in with the Doom Patrol forced him into early retirement. Later, Zahl (now calling himself "General Zahl") assisted Madame Rouge in apparently killing the Doom Patrol in an gigantic explosion. Later it would be known that Robotman survived that explosion, although he was severely damaged.
Many years later, the New Teen Titans, Mento, and Robotman (the only surviving members of the Doom Patrol), tracked down Zahl and Madame Rouge, and with the help of The Brotherhood of Evil, put a stop to their plans. In the conflict, "General" Zahl's bullets ricocheted off Robotman's chest, killing Zahl.