-- Four robotic vehicles finished a Pentagon-sponsored race across the Mojave desert Saturday and achieved a technological milestone by conquering steep drop-offs, obstacles and tunnels over a rugged 132-mile course without a single human command.

The vehicles, guided by sophisticated software, gave scientists hope that robots could one day wage battles without endangering soldiers.

"The impossible has been achieved," cried Stanford University's Sebastian Thrun, after the university's customized Volkswagen crossed first. Students cheered, hoisting Thrun atop their shoulders.

Also finishing were a converted red Hummer named H1ghlander and a Humvee called Sandstorm, both from Carnegie Mellon University. The Stanford robot, dubbed Stanley, overtook the top-seeded H1ghlander at the 102-mile mark.

The sentimental favorite, a Ford Escape Hybrid by students from Metarie, La., was the fourth vehicle to finish. The team lost about a week of practice and some lost their homes when Hurricane Katrina blew into the Gulf Coast.

The Pentagon's Defense Advanced Research Projects Agency, or DARPA, plans to award $2 million to the team of the fastest vehicle completing the race in less than 10 hours. The taxpayer-funded race was intended to spur the development of robots that could be used on the battlefield without remote controls.

The race announcer did not immediately declare a winner because 22 of the 23 robots left the starting line at staggered times at dawn, racing against the clock rather than each other. Stanley finished in less than 71/2 hours. Race officials planned to resume the race Sunday so the sole remaining vehicle, a mammoth six-wheel truck, could compete in daylight.

The Grand Challenge race is part of the Pentagon's effort to cut the risk of casualties by fulfilling a congressional mandate to have a third of all military ground vehicles unmanned by 2015.

Last year's inaugural robot race ended without a winner when all the self-navigating vehicles broke down shortly after leaving the starting gate. Carnegie Mellon's Sandstorm chugged the farthest -- 71/2 miles. Of the 23 robots that competed Saturday, 18 failed to complete the entire 132-mile course, but most beat Sandstorm's mileage last year.

The unmanned vehicles used their computers and sensing devices to follow a programmed route and to avoid hitting obstacles on rough, winding desert roads and dry lake beds filled with overhanging brush and man-made barriers. The machines also had to traverse a narrow 1.3-mile mountain pass with a steep drop-off and to enter tunnels designed to knock out their Global Positioning System signals.

Cornell University's unmanned vehicle traveled about nine miles until it failed to cross a bridge. A robotics fan shows where his heart is during the Pentagon's 2005 Grand Challenge in Nevada.