Humvees loaded with anti-tank weapons and heavy machine guns rolled out on patrol Tuesday from the remote desert base U.S. Marines have established in the Taliban's back yard.

The first Marine contingent had flown in late Sunday, and as reinforcements arrived they saw action almost immediately. Marine Cobra helicopters followed up an airstrike by fighter jets against what appeared to be a reconnaissance column, possibly of the Taliban, late Monday.

Initial reports from the military said the column of about 15 vehicles included tanks. But on Tuesday, one of the Cobra pilots who flew in the nighttime attack said he mainly saw old Soviet-style reconnaissance vehicles.

The pilot, Capt. John Barranco, 30 of Boston, said high-flying aircraft had spotted the column and initially attacked it.

"We watched them engage," said Barranco of the other warplanes, which Central Command officials in the United States had said were Navy F-14 Tomcat jets.

Barranco said his team of Cobras then flew over the target to inspect it, attacked it themselves and then flew over again, using night-vision goggles and infrared sensors to help pick up images in the dark.

"There didn't seem to be anything left of a useful military nature," he said.

In Washington, Pentagon officials said the Marines, expected to total about 1,000 when the deployment is completed, were in Afghanistan to choke off escape routes for Afghanistan's Taliban militia and members of Usama bin Laden's Al Qaeda terrorist network. The officials in Washington added the Marines also will make quick strikes when they can and help identify targets for U.S. bombing.

In daylight Tuesday, the camp seemed busy but calm as the armored vehicles rolled out on patrol. The Taliban seem to prefer dawn and dusk patrols, a Marine said.

The U.S. deployment was still underway from ships in the Arabian Sea and unidentified land bases.

In the sands and dunes around the compound, Marines could be seen in the distance at their outposts.

Apart from securing the area, the soldiers were also racing to set up command centers, accommodation and other facilities. Buildings were marked "medical" or "command."

Out on the runway itself, which is of hard packed sand, helicopters stood ready for takeoff. The sand is so hard and dry that areas have cracked into foot-sized chunks.

The small airport, which the military said was built by a wealthy Arab, is an American base. It is made up of modern, off-white concrete buildings. Tuesday, an America flag flew at the center of the compound.

The military said the field was taken with no resistance and military footage of that mission showed no shots being fired. Many of the buildings, though, were pockmarked with bullet holes, and one building outside the main compound appeared to have been hit by mortars and bullets before Sunday's Marine landing.

The Associated Press was allowed to deploy with the troops on the condition that it did not reveal classified information, troop strengths, mission plans and other secret information.

Task Force 58 was made up of troops from the 15th and 26th Marine Expeditionary Units -- with a normal combined strength of more than 4,000 Marines -- plus other troops for the Afghan deployment, known as Operation Swift Freedom. The units are based on six ships in the northern Arabian Sea.

Capt. Stewart Upton, public affairs officer for Task Force 58, said the Marines want to stress that their mission is not to invade or occupy.

"We are here to rid the people of Afghanistan of the terrorists and to provide them with the peaceful way of life," he said.

Barranco, the Cobra pilot, said after the Sept. 11 terror attacks on the United States he was proud to be part of the mission.

"A family friend was in the World Trade Center, and the last I heard, when I was able to reach home, was still in critical condition. I feel I have a personal stake in this. I feel all Americans have a personal stake in this."