Foreign troops usually take pains to avoid any impression of trampling on religious values in Afghanistan. I have seen Canadian troops burst into suspected Taliban hideouts, searching every corner of the compounds – except the shelf where the family's most treasured possession, the Koran, sits wrapped in cloth.

This is a matter of doing what's right, and also self-preservation. Afghans have a history of violent backlashes against real or perceived threats against the sanctity of their beliefs. This goes back to the days before Islam in the country: it took the Arabs more than two centuries of warfare, on and off, before they fully conquered the territory now called Afghanistan in the year 870, and the Arab invasions were often thwarted by the rebellious locals who resisted the outsiders and their new ideas.

Then as now, Afghans are ready to fight any foreigner who insults their traditions. Mobs of angry men protested in the streets on Tuesday, reacting to news that NATO troops had "improperly disposed" of copies of the Koran. Early reports described hundreds of rioters at the gates of Bagram Airfield, the main American base near Kabul, and later updates said the crowd of "thousands" was trying to storm the perimeter.

Story continues below advertisement

Bagram is heavily defended; there was almost no danger of protesters overrunning the base, in the same way that rioters swarmed over the walls of a United Nations compound in Mazar-i-Sharif last year. In both cases, however, the spark for public anger was mistreatment of Islam's holy book. This is a sensitive issue across the Muslim world but especially in Afghanistan.

The Associated Press quoted Ahmad Zaki Zahed, chief of the provincial council, saying that Afghan labourers at the base noticed 60 to 70 books, including Korans, in a pit used for burning garbage on Monday night. The books were apparently discarded with the trash after being used by detainees at the airbase.

The top NATO commander in Afghanistan, U.S. General John Allen, reacted within hours of the initial reports by issuing a sweeping apology and promising an investigation.

His apology was unusually swift and abject, apparently reflecting NATO's concerns about a violent backlash. No deaths were reported by sunset on Tuesday, but the frenzy highlighted the fragility of plans for Afghanistan. For all of the careful assessments of factors at play in the country, the situation remains prone to sudden shifts. Such volatility becomes more intense with every cultural misstep.