Five are dead—two Americans, three Afghans—after troops in the midst of a "misunderstanding" started shooting at each other.

The Afghan soldier who started the shooting is dead, so it's hard to know what happened. But it sounds like "insider attacks" might be the next stage of the IED: sneaking insurgents into the Afghan army on suicide missions to fire at American troops and cause short-term mayhem and long-term distrust.

Insider attacks this year have increased greatly compared with 2011, when there were 35 over 12 months, arousing concern in the coalition, as well as in Western capitals. French forces announced that they were leaving by the end of next year, a year earlier than originally planned, after losing four of their soldiers in an insider attack in January.

In addition to restricting joint patrols by small units, the military has also required its forces to wear body armor and carry loaded weapons whenever they are in the presence of Afghan forces...

A senior American military officer said recently that only a fourth of the insider attacks could be definitely linked to insurgent infiltration of the Afghan security forces, and another fourth were judged to have been caused by personal disputes. The rest, however, usually resulted in the death of the perpetrator and it was unclear what the cause was.

It's a devilish and clever strategy to keep the chaos rolling and stymie efforts at coalition- and nation-building. The Taliban's greatest enemy is a stable, secular, viable alternative to their way of ruling the country.