Six U.S. service members died in separate attacks in Afghanistan on Saturday, another round of killings in what is shaping up to be the most violent summer of the nearly nine-year war.

Poor marksmanship is the least of it. Worse, crooked Afghan cops supply much of the ammunition used by the Taliban, according to Saleh Mohammed, an insurgent commander in Helmand province. The bullets and rocket-propelled grenades sold by the cops are cheaper and of better quality than the ammo at local markets, he says. It's easy for local cops to concoct credible excuses for using so much ammunition, especially because their supervisors try to avoid areas where the Taliban are active. Mohammed says local police sometimes even stage fake firefights so that if higher-ups question their outsize orders for ammo, villagers will say they've heard fighting.