During the events of Modern Warfare 2, Lieutenant General Shepherd betrayed Task Force 141; subsequently all the remaining members were either eliminated or on the run, the rogue Shepherd was then killed by John "Soap" MacTavish at the conclusion of the crisis and Task Force 141 was disavowed.
He does not hesitate to do good things if it benefits him, but he can also easily betray allies for his personal gain. Phillip Graves was a complex villain with antihero qualities in Modern Warfare 2, and that is most likely to continue in the Modern Warfare 3 campaign.