A problem that rendered as many as 10,000 U.S. military GPS receivers useless for days is a warning to safeguard a system that enemies would love to disrupt. The Air Force has not said how many weapons, planes or other systems were affected or whether any were in use in Iraq or Afghanistan. But the problem, blamed on incompatible software, highlights the military's reliance on the system and the need to protect technology that has become essential for protecting troops, tracking vehicles and targeting weapons.

 

The problem occurred when new software was installed in ground control systems for GPS satellites on Jan. 11, the Air Force said. Between 8,000 and 10,000 receivers could have been affected, out of more than 800,000 in use across the military. The Air Force initially blamed a contractor for defective software but later said it was a compatibility issue rather than a defect. At least 100 U.S. defense systems rely on GPS, including aircraft, ships, armored vehicles, bombs and artillery shells. Because GPS makes weapons more accurate, the military needs fewer warheads and personnel to take out targets. But a GPS-dependent military becomes vulnerable if the technology is knocked out.