With the arrival of a C-130 transport plane, Iraq's second-largest airfield Thursday took on a crucial role in U.S. war strategy: a way to sidestep Iraqi attacks on supply lines and get the troops what they need.

Tallil airfield -- mothballed since the 1991 Gulf War -- was captured Saturday by U.S. soldiers and is now an important forward base on the way to Baghdad. Supplies and men can be delivered here without having to travel by ground from Kuwait and risk bloody encounters with Iraqi forces still roiling the south.

A hastily posted sign declared the airfield as "Bush International Airport." The immediate goal was to speed all the stuff of war -- fuel, ammunition, water, food, reinforcements -- to the front, shortening supply lines that had extended as much as 200 miles into Iraq.

There were reports of some shortages Thursday, as U.S. and British troops continued to encounter unexpectedly fierce resistance throughout the south. Some Marines were being issued two meal packets every 36 hours; normally, they get three meals a day.

Brig. Gen. Vincent Brooks, a spokesman for the central command, said he had not heard of any shortfalls of supplies. "We haven't had any problems that would hinder operations at this point," he said.

He insisted that war plans were working.

But the fight continued around An Nasiriyah, the key city on the Euphrates River. More than 25 Marines were wounded in fighting there, and U.S. officials said some or all of them were hurt when one Marine unit mistakenly fired on another.

"There are a lot of forces out there that still want to fight. They didn't exactly roll over and surrender," said a Marine helicopter pilot who would use only his nickname, Lurch. "We are so wrapped up in not creating collateral damage that we are leaving great enemy strongholds behind."

Fighting continued at Basra, as well, and at Najaf, less than 100 miles from Baghdad, where units of the Army's 3d Infantry Division had encircled the city and were fighting Iraqi reinforcements from Baghdad, according to Steven Lee Myers, a New York Times reporter who spoke on CNN.

The 1st Brigade of the 101st Airborne Division started arriving at a forward operating base in southern Iraq within striking distance of Baghdad -- the first of about 20,000 soldiers in the air assault division expected to join the fray.

In the north, cargo planes delivered military supplies a day after 1,000 American airborne troops parachuted in to seize an airfield.

The seizure of Tallil and the northern airfield is "not only a monumental step forward but absolutely essential," said military analyst John Abrams, a retired Army general.

For the moment, controlling the bases instantly and dramatically shortens supply lines, reducing their dependence on hundreds of miles of roads where convoys were exposed to hit-and-run attacks by Iraq's Fedayeen and other irregular troops.

From these bases, supplies and troop reinforcements -- like the Army's 4th Infantry Division (Mechanized), 30,000 highly mobile troops who will be deployed from Texas in coming days -- could be airlifted further by helicopter, or sent overland faster and with far less danger.

But Abrams said U.S. control of the bases also reduces Iraq's capacity to counterattack. It will allow use of special radar networks to protect against airborne suicide bombers, helicopters or other aircraft, including RPV drones that could be used for chemical attacks on U.S. troops.

Being able to deploy easily and quickly from forward bases "at a time and place of their own choosing," U.S. commanders will gain the element of surprise and "keep Saddam guessing, forcing him to look in all directions," Abrams said.

The northern airfield taken by 173rd Airborne Brigade paratroopers gives the United States an alternative to bases that Turkey denied. It has a 6,700-foot runway and can accommodate the largest U.S. heavy-lift cargo planes.

The same is true of the sprawling Tallil base, which is located just four miles from An Nasiriyah. U.S. military officers said Tallil was the country's largest airfield after Baghdad's international airport.

Its main runway, once used by Iraqi jet fighters, is long enough to take the military's largest transports as well as civilian 747 jumbo jets.

"It's been sitting in a time warp waiting for someone to wake it up," said Col. A. Myers of the U.S. Air Force Air Mobility Command. His unit, from Scott Air Force Base in Illinois, had the mission to revive it.

It took five days to clear its 12,000-foot runway of concrete blocks, wrecked vehicles and other barriers placed on the strip by the Iraqi military to prevent its use.

The air base had been only partially occupied and maintained over the past decade. Jumbles of rusting equipment were strewn around the derelict control tower and American troops were clearing out ramshackle buildings before moving in.

Located within southern Iraq's no-fly zone, Iraqi aircraft had not used the airfield since it was heavily bombed during the Gulf War. Myers, of Kissimmee, Fla., said U.S. army engineers had to clear the area of unexploded American bombs as well as Iraqi mines and other ordnance.

Blasts from bombs and other weaponry being destroyed could be heard throughout the day Thursday.