The killing of Hamid Karzai's brother means the war in Afghanistan is going worse than we thought.

This failure was an obstacle in the war—perhaps the biggest obstacle—before the recent spate of assaults and assassinations. It's a still bigger one now.

The Taliban are not very popular, but they don't have to be. Many Afghan people remember the harshness of the Taliban's rule. Many may also know (though this is less certain) that the dramatic rise in civilian casualties in the past six months is the result primarily of the Taliban. (A United Nations report estimates that the Taliban—not U.S., NATO, or Afghan security forces—are responsible for 80 percent of these casualties.)

But this doesn't matter. The beleaguered Afghan people aren't going to risk their lives for their government if their government can't provide them security. And that's why the killings of the past week, piled on top of the regime's many other failures and shortcomings, may bode ill for the course of the entire war.

Correction, July 18, 2011: This article originally misreported Gen. John Allen's first name. (Return to the corrected sentence.)