Fred Kaplan writes: The game is over in Afghanistan. An American presence can no longer serve any purpose. Or, rather, it can only extend and exacerbate the pathologies of this war. It is time to get out, and more quickly than President Obama had been planning. The consequences of leaving may be grim, but the consequences of staying are probably grimmer.

Sunday’s massacre in Kandahar province, in which a veteran U.S. Army staff sergeant sneaked out of his base at 3 a.m., strolled into a village, and methodically gunned down 16 Afghan civilians, including nine children, is but the latest sign of a massive unraveling.

Two weekends earlier, an Afghan gunman killed two U.S. officers inside the Interior Ministry’s headquarters (making the ninth and tenth Americans who have lost their lives this year at the hands of Afghans they’d been training). Shortly before then, violent riots broke out when Americans were discovered burning copies of the Quran. Just two days before the Kandahar rampage, NATO helicopters flying over Kapisa province, in eastern Afghanistan, fired on a group of civilians, killing four and injuring three, prompting large street protests.

Finally, the New York Times reported over the weekend that Afghan president Hamid Karzai is starting to enforce a law banning the use of private security guards to protect foreign business and aid workers, requiring that Afghan police be used instead. Even before the incident in Kandahar, Western officials were predicting that the new law would force a shutdown of nearly every development project; no civilians would want to stick around without someone reliable guarding their backs—and after the string of incidents, no Afghan can be regarded as reliable, any more than Afghans can regard any American as reliable.

And there’s the problem. The U.S. and NATO strategy in Afghanistan relies on building trust, and those bonds of trust—always tenuous at best—are now severed, perhaps irreparably.