The massacre which a lone U.S. soldier allegedly committed this week in Afghanistan, killing 16 Afghan civilians, has nothing to do with America's policy in that troubled country.
But the tragedy must cause U.S. officials, from President Obama on down, to consider whether our country is likely to gain anything more from continuing to maintain about 90,000 troops in Afghanistan.
We certainly have much to lose.
More soldiers added to the death toll of 1,800, of course. But also at stake is all the U.S. has achieved during the longest war in its history.
al-Qaeda's power is diminished. Osama bin Laden is dead. Afghanistan has established a republic - albeit a tenuous one.
But incidents such as this week's murders, and the recent burning of Qurans by troops at a U.S. base, greatly increase the risk that whatever gratitude among Afghans our sacrifices have engendered will be replaced by resentment and anger.
Obama's current time line calls for removing the last U.S. troops by the end of 2014. That's almost three years away.
And it might be too far.