From his first campaign for president, Barack Obama promised to end more than decade of war and bring American troops home. Yet he has since scaled this back to withdrawing "combat" forces, thus allowing him the loophole of retaining up to 12,000 U.S. forces in the country. Yet Karzai's insistence that all U.S. raids on Afghan homes by such residual forces be stopped shows that Obama has simply redefined the word "combat." Counterterrorism missions do involve extreme danger and shooting people -- combat in the thinking of any layman. U.S. military forces training Afghan forces in the field can also be involved in what anyone would recognize as combat, especially if they come under enemy fire. So in reality, by leaving any U.S. forces in Afghanistan, Obama is really breaking his promise to the American people to remove all combat forces by the end of 2014.

But are these residual forces really needed for U.S. security? Hardly. Even U.S. intelligence believes only a small number of al Qaeda operatives remain in Afghanistan. If the United States needed to kill them, it could simply do so with airstrikes or drone attacks from outside the country. The real reasons for the continuing presence of U.S. forces is to keep training the wobbly Afghan security forces and act as a political symbol of continued American commitment to the Afghan government's survival. Since a 12-year, $43 million "train and equip" mission by a larger U.S. force has not resulted in competent Afghan security forces, it is doubtful that a smaller residual American force can effect the same. In other words, the main reason the troops are being left appears to be that if the United States left completely, psychologically the Afghan regime would collapse and civil war would resume. Newsflash: That outcome may happen even if the United States keeps a residual force in the country, only resulting in more needless American deaths.

At any rate, given those dire circumstances, one would think that Karzai would be pandering to the Americans to get them to stay rather than milking them for every possible concession. However, Karzai knows how Americans think. Unfortunately, he knows that in the past, they have behaved imperially, rarely leaving anywhere they have occupied, because they foolishly believe their security depends on remaining in far-flung places around the globe to conduct nation-building missions. So he brazenly makes more demands of the United States, even while his government's future is tenuous without -- and maybe even with -- residual American forces and aid.

The Obama administration should abandon the American imperial way of thinking and use Karzai's escalating demands -- and refusal to sign the bilateral agreement until next spring -- to call his bluff and withdrawal American forces completely from Afghanistan. The United States doesn't need troops on the ground in the country to prevent any return by al Qaeda, taking advantage of the return of chaos, but only to warn the Afghan Taliban not to harbor such people or American air power will return to pummel the country from the air. That threat is credible and should deter a Taliban that likely has learned its lesson from sheltering such unwanted visitors the last time around.