IN THE SKIES OVER NORTHERN IRAQ - Nearly 1,000 U.S. Army paratroopers jumped out of low-flying jet airplanes in the dark of night yesterday and took control of an airfield in Iraq's Kurdish-controlled region.

This marks the first large coalition ground force in northern Iraq, which could open another front against Saddam Hussein's regime.

The mission by the 173d Airborne Brigade was the 29th combat jump in U.S. history, brigade officers said. The paratroopers, many of whom are elite Army Rangers, flew directly from an air base in Europe.

Fifteen Air Force C-17 Globemaster transport planes dropped troops and equipment in the vicinity of an airstrip dubbed Objective Buford near the city of Bashur, 30 miles from the Turkish border. The men had trained to jump at an altitude of about 500 feet and hit the ground at speeds of up to 17 m.p.h. Commanders on the ground said there were no serious injuries.

The parachute drop, assisted by U.S. special operations soldiers working with Kurds on the ground, was designed to establish an American combat force in a region laced with ethnic tensions, said Col. William Mayville, the 173d's commander.

"I think our presence will act as a stabilizer," Mayville said. "Our presence changes the dynamics of the environment."

Four rows of jumpers sat arrayed on each transport plane, two rows per jump door. When the light turned from amber to green, the men moved to the door at a fast pace, given the heavy rucksacks they carried.

In Chalk Six, the name given to the sixth C-17 in the formation, at least two paratroopers stumbled as they ran to the door. But the jump "safeties" - two men whose job means what it says - pushed them out. In 60 seconds, the light was red, and every jumper in Chalk Six - all 99 - was gone.

The Kurdish-held enclave of northern Iraq has been protected by U.S. and British jets from Iraqi attack since the first Gulf War as a no-fly zone.

The Bashur airfield was chosen because it could handle repeated landings by the 174-foot C-17s, Mayville said. The brigade decided to conduct an initial parachute drop rather than ferry troops in by plane because an air assault ensured that a significant combat force could form almost immediately to protect itself, officers said. On Tuesday, 173d commanders said they were told that a special-forces "A" team was overrun by 100 Iraqis in Irbil, about 35 miles from the drop zone, also within Kurdish-held Iraq.

"Nobody wants war," said Lt. Col. Dominic Caraccilo, commander of the Second Battalion, 503d Airborne Infantry, one of the brigade's two infantry battalions. "But this is a paratrooper's dream."

The 173d's operation is a major departure from the Pentagon's original plan for northern Iraq, which called for the Army's heavy Fourth Infantry Division, with hundreds of tanks and sophisticated heavy weapons, to move into the north from a staging ground in Turkey. The 173d, a light infantry unit that lacks armor, was slated to join that effort.

But the Turkish government declined to grant permission for U.S. troops to stage from its soil, so Central Command changed the plan. The drop zone, within an autonomous Kurdish enclave, was considered "permissive," meaning the soldiers didn't expect to be shot at as they descended to Earth with enough gear, food and water to survive for several days.

But commanders remain deeply concerned about a potential threat from Ansar al Islam, a militant Kurdish Islamic group operating in the north. Kurdish officials say dozens of Osama bin Laden's fugitive followers, most of them Arabs, have found refuge with Ansar.

"Don't underestimate what a big deal this is," Caraccilo told his troops as they rehearsed the operation last week.

This reporter, embedded with the 173d Airborne Brigade, was present during final mission rehearsals and was on one of the massive transport planes from which troopers jumped.

The brigade is to establish its base of operations around the airfield. Future missions could involve protecting key northern oil fields or ousting pockets of Iraqi resistance. But among the force's main roles is to keep peace among long-feuding Kurdish factions - and to separate the Kurds from any Turkish troops that may cross into Iraq.

As a result, the young soldiers will have to make careful decisions about the use of force in an area where men carrying rifles are a feature of the landscape - but not necessarily a threat to the Americans.

If American troops hope to guard against Kurdish separatist inclinations, they are also there to dissuade Turkey from making any bold moves in Northern Iraq, commanders said.

Among Turkey's large Kurdish population is a minority of violent extremists who have pressed for an independent Kurdistan, and Turkey has sometimes used brutal methods to suppress them. Turkey has threatened to invade if the Kurds try to establish an independent state.

The troops jumped with their Alice rucksacks attached to their waists, packed to the gills with ammunition and gear - including three MREs, six quarts of water, a Kevlar helmet, a protective mask and chemical suit, knee pads and wind goggles. Some carried radios and machine gun parts.

When they were about 100 feet from the ground, they were to release their packs on a 15-foot rope so those hit the ground first.

For the rest of their essential equipment, including their body armor and additional cold-weather gear, they had to pack a separate duffel bag known as the "A" bag, which was expected to arrive in a separate plane a few days after the jump. A third bag called the "B" bag is filled with nonessential items such as running shoes. The troops are convinced they will never see their "B" bags.

All the same, said Spec. Jonathan Bourne, 25, of Myrtle Beach, S.C., "I think we're making history. Making history and changing the world."