They 'swore' (an oath of) allegiance to the United States of America. [=they formally promised that they would be loyal to the United States of America]
He 'swore us to secrecy/silence'. [=he made us promise not to tell anyone his secret]
He was so disgusted by the election results that he 'swore off' politics for good.
(..) the true enemy won't wait out the storm. He brings the storm. Your son was butchered at the Red Wedding, Lord Manderly, but you refused the call. You swore allegiance to House Stark, Lord Glover, but in their hour of greatest need, you refused the call. And you, Lord Cerwyn, your father was skinned (..)2016 TvShow: Game of Thrones Title: The Winds of Winter Season: 6 Episode 10