the campaign is not free, the game consists of warzone, campaign and other, only warzone is free to play, you need to purchase the full game to access all the other content.
Good news for fans of the classic CoD BR, Warzone 1 is still playable under the new guise of 'Warzone Caldera.' Warzone 1 was temporarily offline when the sequel first arrived, but around a week later the servers came back and the rebrand as Warzone Caldera was complete.