It had been a long wait for the NATO troops poised here on Macedonia's frontier with Kosovo.

For much of Friday, the armored vehicles of the King's Royal Hussars battle group had sat, stalled, just across the border from the winding two-lane highway that leads to Pristina, Kosovo's capital, where the unit plans to secure the airfield as the headquarters of NATO's intervention in the Serbian province. The unit's 630 men and women have been training since late February to make the 40-mile drive, preparing for roadblocks, angry Serbian civilians, hidden land mines and casualties.

But the schedule for their trip changed repeatedly. With NATO's 11-week bombing campaign ended and an agreement for the withdrawal of Yugoslav troops from Kosovo in hand, it appeared for a while that the King's Royal Hussars would be the first armored unit to cross the border Friday afternoon. But their British commander was instead instructed to hang back and give Yugoslav forces in southern Kosovo more time to move north.

It was the latest twist in a military plan that appears to have been rewritten every few hours. First members of the unit were told they would enter Kosovo Friday morning; then they were told of a 24-hour delay to give U.S. Marines who had been stationed offshore on warships for the past few months a chance to join the head of the column. The Marines were not ready but insisted on not being left behind, several soldiers here said.

The wait was complicated even more by news that a Russian convoy had appeared unexpectedly in Pristina at 1:30 a.m. local time, hours before the first NATO contingent was scheduled to start the trek north. There were some reports that the Russians were taking up positions at the Pristina airport that NATO forces had planned to secure.

"We've been here for three months and waiting a long time," all the while hearing alarming accounts of the actions of Yugoslav government forces in Kosovo, said a senior officer of the battle group, while standing in front of dozens of Challenger heavy tanks, Scimitar light tanks and Warrior personnel carriers lined up in neat rows on the hill. "They are dying to get in there."

As various NATO units filtered onto the road Friday between the border and Macedonia's capital, Skopje, streets were flooded with military vehicles from the United States, Italy, France, Britain and other allies -- although only 19,300 of the 50,000 troops that allied forces said they needed for operations in Kosovo had arrived so far.

Special forces units from several NATO countries are thought to already be in Kosovo, providing intelligence on the departing Yugoslav troops and arranging meetings with key commanders of the Kosovo Liberation Army, the rebel group that has been fighting for Kosovo's independence from Serbia, the dominant republic of Yugoslavia.

As dusk fell, the troops settled into a comfortable routine. Like suburbanites anywhere, they read books, prepared dinner, listened to the radio, took group photos and lounged on cushions beside their vehicles. But their vehicles happened to be some of the most lethal machines imaginable, with 30mm and 120mm cannons or submachine guns.

A slogan painted on the front of the light tank slated to go across the border first, No. 21A, warns onlookers to "Repent." Its commander, Cpl. Alan Sheppard, said, "We are ready for anything: mines, obstructions and especially withdrawing VJ forces." VJ is the Serbian denotation for the Yugoslav army. But Sheppard added that the prospect of meeting Russian soldiers in Pristina -- as British intelligence officers had predicted -- came as a surprise.

"The Russians are our allies now. They just slightly jumped the gun on us," Sheppard said. Asked what he would do if he encountered a Russian who arrived in Pristina before him, the unit's senior commander said: "I think I'd go up and shake his hand and talk about it. We don't have any rules of engagement with the Russians."

Hours later, a colleague strode up and informed him that the intelligence reports of Russians entering Kosovo were erroneous. Before dawn this morning, as footage of Russian troops entering Pristina was being shown on television sets around the world, intelligence reports available here still maintained that the Russians had not yet entered the province.

Several officers said they expected a warm welcome from members of the Kosovo Liberation Army, which has long called for NATO's deployment in Kosovo to keep peace. But the soldiers were expressly ordered by a commander at a final briefing to be sure to act even-handedly once they arrived and to be prepared to take action against any KLA members who violated the cease-fire.

To reach the camp here at Brazda, the battle group drove along a highway through the heart of Skopje, partly to avoid traffic and partly because fewer local residents would be around to observe and possibly to interfere with the convoy. Most Macedonian residents are ethnic Slavs and have relatives in Serbia; many openly hold ethnic Albanians in low esteem.

During the drive, some residents flashed the Serbs' traditional three-fingered victory salute, and children in a group of Gypsies -- a minority in Kosovo that has been sympathetic to the Yugoslav government -- threw stones at passing vehicles. But in a predominantly ethnic Albanian neighborhood along the route, the convoy's passage got the same reception as a Fourth of July parade. Fathers hoisted children onto their shoulders and their wives joined in chanting "NATO" and "Kosovo."

Across the border, Kacanik -- the first town in Kosovo that the convoy is expected to reach on Saturday -- was in flames Friday, torched by departing Yugoslav forces, according to several officers.

Correspondent Molly Moore in Skopje, Macedonia, contributed to this report.

CAPTION: A convoy of Russian armored vehicles bearing the freshly painted initials of the NATO-led peacekeeping force for Kosovo travel along a highway near Belgrade, the Yugoslav and Serbian capital.

CAPTION: British Lt. Gen. Mike Jackson has promised to protect all Kosovars.