The new troops will be embedded with Iraqi troops:
The vast majority of them — five brigades — will be deployed to Baghdad. These troops will work alongside Iraqi units and be embedded in their formations. Our troops will have a well-defined mission: to help Iraqis clear and secure neighborhoods, to help them protect the local population, and to help ensure that the Iraqi forces left behind are capable of providing the security that Baghdad needs.
And the enemy is Al-Qaeda and its plan for a “radical Islamic empire”:
As we make these changes, we will continue to pursue al Qaeda and foreign fighters. Al Qaeda is still active in Iraq. Its home base is Anbar Province. Al Qaeda has helped make Anbar the most violent area of Iraq outside the capital. A captured al Qaeda document describes the terrorists’ plan to infiltrate and seize control of the province. This would bring al Qaeda closer to its goals of taking down Iraq’s democracy, building a radical Islamic empire, and launching new attacks on the United States at home and abroad.
And then there’s this:
Succeeding in Iraq also requires defending its territorial integrity – and stabilizing the region in the face of the extremist challenge. This begins with addressing Iran and Syria. These two regimes are allowing terrorists and insurgents to use their territory to move in and out of Iraq. Iran is providing material support for attacks on American troops. We will disrupt the attacks on our forces. We will interrupt the flow of support from Iran and Syria. And we will seek out and destroy the networks providing advanced weaponry and training to our enemies in Iraq.
Text of the Bush speech here.