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.
(..) Dialogue: Marked=..,Default,NTP,!Effect,...that you have been accepted at\NHogwarts School of Witchcraft and Wizardry.'' Dialogue: Marked=..,Default,NTP,!Effect,He will not be going there! We swore when we took him in\Nwe'd put a stop to all this rubbish. (..)2001 Harry Potter and the Sorcerer's Stone