Modern Warfare 2's campaign mode is made up of a total of 17 story missions, each with different time requirements. In total, if you focus only on the main story, you will spend around 6-8 hours on average to complete the game.
He is originally an ally to Task Force 141, but due to them coming closer to finding out the truth about the American ballistic missiles that Graves and Shepherd lost, Graves betrays the team on Shepherd's orders. After he escaped from the JTF-Ghost Team, Graves went hiding.