Marc Lynch on the Ft. Hood shooting:
The grand strategy of al-Qaeda and its affiliated ideologues is, and has always been, to generate a clash of civilizations between Islam and the West which does not currently exist. Their great challenge is that the vast majority of Muslims reject their theology, ideology, strategy and tactics. That's especially true of American Muslims. They therefore feel the need to change the environment in which Muslims live in order to change their calculations about the appropriateness of extremist identities and ideologies and actions.
Terrorism is a means towards that end. The object is to create a violent, polarized environment in which Muslims are forced to embrace a narrow, extreme version of Muslim identity. They want Muslims to accept a master narrative in which the Islamic umma is existentially threatened by Western aggression, and the only theologically and strategically appropriate individual response is to join the jihad in the path of god (as they have defined it).