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.
(..) smell a fraud from a mile away. Useful talent. I'm here for my grandson and granddaughter. Your grandson and granddaughter swore sacred vows and lied. The Father judges us all. Sons of high lords, sons of fishermen. If you break his laws, you will be punished. (..)2015 TvShow: Game of Thrones Title: The Gift Season: 5 Episode 7