The New York Times reports that President Obama will announce tonight that he will withdraw 10,000 troops from Afghanistan this year, and another 20,000 by the end of next summer. At that point the 30,000 additional troops Obama committed to Afghanistan in 2009 will have been returned. 

According to the Times, this will be a more aggressive drawdown than what Gen. David Petraeus recommended. Furthermore, 

It amounts to a broad rethinking of the military’s troop-intensive counterinsurgency strategy that Mr. Obama adopted 18 months ago after a painstaking review. Officials have indicated that the administration now plans to place more emphasis on focused counterterrorism operations of the kind that killed Osama bin Laden – which the president is expected to cite as Exhibit A for a substantial American drawdown. 

In other words, this drawdown was made possible by the killing of Osama bin Laden. Without that, the president would have had a harder time making the case for overruling Petraeus and co.