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.
(..) - Want to see the apple trees? - She thinks that Babe can really talk. Contemporary political fiction? - Yes. Good. - I swore this semester would be different. I would get to class on time. Finish my assignments on time. I would do everything on time. I left my purse on the bench. (..)2004 TvShow: Gilmore Girls Title: The Nanny and the Professor Season: 4 Episode 10