Claiming progress in the war against the Taliban and Al Qaeda, President Obama declared Wednesday that he would withdraw all 33,000 “surge" forces he had authorized 18 months ago, with the initial 10,000 troops leaving Afghanistan by the end of the year.

Obama's troop drawdown plan was much quicker and larger in number than recommendations by his most senior military commanders who fear a rapid draw down could undo security gains in southern Afghanistan and hamper forthcoming offensives against the Haqqani Network and Al Qaeda terrorists in the east.

"This timeframe will only serve to undermine U.S. efforts to defeat the Taliban and Al Qaeda and stabilize Afghanistan." -- Ahmad Majidyar

Just as the troop withdrawal deadlines he called for during his campaign, and then later as president in a speech at West Point when he unveiled his new Afghanistan strategy in 2009, Obama's calibration of strategy with a greater focus on politically-motivated deadlines and less emphasis on security realities on the ground is a strategic mistake.

The president tried to rationalize his military timelines in 2009 by arguing that a troop withdrawal deadline would pressure Afghan President Hamid Karzai to curb corruption and improve governance. But the effect was opposite.

Obama's initial pledge to withdraw troops by 2012 further undermined the effectiveness of the surge. The president's strategy emboldened the Taliban, strained ties with Kabul, and convinced Pakistan that continued support for the Taliban would be the best strategy to wield influence in post-withdrawal Afghanistan.

Instead of learning from his past mistakes, the president has done the opposite. Mr. Obama has now succeeded in laying out a new and unrealistic timeframe to bring the war in Afghanistan to a close. This timeframe will only serve to undermine U.S. efforts to defeat the Taliban and Al Qaeda and stabilize Afghanistan. It will also, ultimately, cost more American lives.

Both the 2011 and 2012 timeframes for troop reductions coincide with the fighting season in Afghanistan. Troops will begin leaving Afghanistan next month as violence in that country is at its worst in nine years and the Taliban reasserts itself in territories U.S. forces have abandoned.

The deadlines will also weaken the coalition in Afghanistan. Our allies will use Obama's withdrawals to provide diplomatic cover for their own forces. British Prime Minister David Cameron will use Obama's declaration of progress in Afghanistan to justify his own troop withdrawals. Canada, Holland, and Poland and many other countries have also announced their own withdrawal dates. It will now be difficult for Washington to convince allies to contribute the troops needed not only to win in Afghanistan, but simply to maintain progress there.

The deadlines also have negative psychological implications. After three decades of conflict, survival is a priority for Afghan leaders and tribesmen, who will not risk backing the United States and the Afghan government if they think Washington will leave them at the mercy of Taliban retribution. In Iraq, tribal chiefs cut ties with Al Qaeda and allied with the United States because the Bush administration pledged it would not abandon them. Obama has made no such commitment to our Afghan allies.

Alas, the president's hasty withdrawal plan not only gives the Taliban an incentive to retrench and hold on to their arms, but Mr. Obama has now justified the terrorists' belief that America may have the clocks, but they have the time.

Ahmad Majidyar is a senior research associate at AEI.