He was a 'traitor' who betrayed his country by selling military secrets to the enemy.
He 'turned traitor'. [=he became a traitor; he betrayed his country/friends]
She has been called a 'traitor' to the liberal party's cause.
(..) Solely won. The people. Rose up from the ashes and a new era was born. The freedom has a cost. And the traitors was defeated. Peace-War as a nation. We would never know this treason again. And so, it was decreed... That each year. (..)2012 The Hunger Games