More troops and equipment arrived at a secret U.S. Marine base in southern Afghanistan on Wednesday, with military officials reporting a quiet night on the base perimeter.

The Marines seized this airstrip within striking distance of the Taliban stronghold of Kandahar in a nighttime raid on Sunday. Cobra helicopter gunships had engaged a column of 15 suspected hostile vehicles on Monday night after high-flying aircraft identified it and bombed them. The Cobras followed up with their own attack, and pilots involved said there was no evidence of any military threat after the engagement ended.

On Wednesday, Capt. David Romley, a spokesman for Task Force 58, said the night had been quiet on the base's perimeter. Helicopters and C-130 aircraft landed through the night to bring in reinforcements.

The base is a modern complex of buildings, where construction appeared to have been underway. There was evidence, such a bullet holes in the white concrete walls of the buildings, of previous fighting.

"The Marines have clearly strengthened their positions," Romley said after a morning staff briefing. "There were no engagements on our perimeters, however we continue to flow in additional personnel, equipment and ordinance."

Marines were calm but busy at the dusty base set up for Operation Swift Freedom, while those who could be seen on the surrounding sand and dunes kept a constant lookout from outposts and patrols.

The Marines have refused to say how many troops it had on the ground, and it was not possible to estimate because many of the units were in the field.

In Tampa, Fla., on Tuesday, the commander of the U.S. war effort, Gen. Tommy Franks, said that by the time the deployment is complete, between 800 and 1,100 Marines will be at the base located near Kandahar, the last city held by the Taliban.

Franks said the "forward operating base" was intended "to give us a capability to be an awfully lot closer to the core objectives we seek" -- destruction of the routed Taliban militia rulers and Al Qaeda, the terrorist network it is accused of harboring. Among the Marines' missions, Franks said, would be watching roads for fleeing Taliban.

The United States hold Al Qaeda and its leader, Usama bin Laden, responsible for the Sept. 11 terror attacks on New York and Washington.

While the Marines' presence "does in fact provide pressure" against Kandahar, they were not deployed for an assault on the city, Franks said. The Marines could be stationed at the base for more than 30 days, he said.

The deployment, dubbed Task Force 58, is made up of the 15th and 26th Marine Expeditionary Units, which normally number more than 4,000, plus other troops. The two units are based on six ships in the northern Arabian Sea. Troops were being flown in from the ships and from secret air bases on land.

The Associated Press was allowed to deploy with the Marines on the condition that it did not report on troops strengths, mission plans, the location of the base or on other secret material.