About 8,000 Marines are expected to go in first, followed by about 9,000 Army troops.
The additional forces only partly answer a standing request from the U.S. commander in Afghanistan, General David McKiernan, who has sought as many as 30,000 additional U.S. forces.
The United States has slightly more than 30,000 troops in Afghanistan now.
More importantly, Obama seemed to be unaware of recent developments in Pakistan now that the government there has conceded ground to the Taliban.