Several suicide bombers blew themselves up in two cities Sunday, killing 13 members of Afghan security forces. Five assailants were also killed. In Kunduz, they targeted an army recruitment center, where the attack led to a lengthy gun battle. At least 20 recruits were also injured. And on the edge of Kabul, another group of Taliban fighters led an ambush against an army bus. The attacks seem to have been conducted as a deterrent to Afghans joining the domestic security forces, which currently number about 250,000, as part of a massive recruitment effort. The Taliban has also been sending letters to civilians, warning them to prevent sons and other relatives from enlisting.