Given a sentence and two mentions from the text (arguments), indicate a phrase (a verb or noun phrase) that describes the relationship between the provided arguments.

Sentence: 'Current Broncos head coach Mike Shanahan coached the Raiders before being fired just four games into the 1989 season , which has only served to intensify this rivalry .', Argument/Subject 1: 'bronco', Argument/Subject 2: 'mike shanahan'
fire

Sentence: 'The African Union is a successor to the Organization of African Unity .', Argument/Subject 1: 'african union', Argument/Subject 2: 'organization of african unity'
be successor to

Sentence: 'President Abraham Lincoln appointed Edwin M. Stanton of Ohio to be his new Secretary of War .', Argument/Subject 1: 'secretary', Argument/Subject 2: 'president'

be appoint by