Task: Question Understanding
Input (English): Context : William Blagheen (born 1832, date of death unknown), also known as William Blagden, was a Union Navy sailor in the American Civil War and a recipient of the U.S. military's highest decoration, the Medal of Honor, for his actions at the Battle of Mobile Bay. 
Question : What armed force did William Blagheen serve in?
Output (English): military branch