The ethnic cleansing of Kosovo was planned in great detail many months in advance, long before the peace talks began in France in February, and carried out with an efficiency that would have put Nazi Germany to shame, say Nato analysts.

As hundreds of thousands of refugees pour across the borders of Macedonia and Albania, the shape of the operation which threatens to empty Kosovo of nearly two million ethnic Albanians is starting to emerge. Although controlled from Belgrade, its command headquarters was in Kosovo's capital, Pristina, the last place to be "cleansed". The operation was spearheaded by Serbian army units, who drove south into Kosovo from Serbia proper. Soldiers and police in uniforms and black masks, along with irregulars made notorious from the other Balkan wars - savages armed with knives, grenades and guns - ran riot in Kosovo.

From Mitrovica, in northern Kosovo, the ethnic cleansers split into two, moving down the east and west sides of the province. First, they concentrated on the half-dozen larger urban areas, such as Pec and Prizren in the west and south, and Gnjilane in the east, separating the Albanians in between into pockets.

Pec, a city close to the border with Montenegro, was the first to be ravaged, and the pattern set there was repeated across Kosovo. The same stories recur of armed men banging on doors, bursting in and firing into the ceiling or the walls, cursing and screaming and ordering Albanians to leave on pain of death. Most people were given a few minutes to pack up and get out.

South and east from Pec, many buildings in the town of Djakovica were razed, say the refugees, trapping some people who were burnt alive. Again, the pattern of eviction was the same, with soldiers shouting the same phrases over and over: "You wanted Nato, now go and ask them for help." Or: "This is Serbia. You wanted Albania, so go there." The same was happening in the east.

After advancing southward, both major assault forces turned towards each other, completing a large pincer movement through the mountains of central Kosovo to meet at a point just south of Pristina, thereby encircling the city. Along the way the two large main forces split into small operational units, backed by tanks, to wipe out the hundreds of ethnic Albanian villages, hamlets and communes. Houses were set ablaze and the peasant farmers who lived in them were driven off to the west and south.

The tactics used in the larger urban areas were identical. After hours of shelling by tanks and mobile artillery, the units of the much-feared MUP Interior Ministry troops, using light machine guns, mortars and armoured personnel carriers, moved in to do the dirty work. MUP gunmen and their even more venomous special duty offshoot, the PJP, have nearly 10,000 troops, backed by 8,000 reserves. Working in battalion strengths of 800 troops, their job was to drive all Albanians into the street and round them up, before pushing them into the countryside. They also robbed them of money, jewellery and papers.

But not everybody was allowed to leave. Many young males between 16 and 35 have simply disappeared, especially from main urban centres. Also missing are the ethnic Albanian elite, the lawyers, doctors, teachers and journalists. They were weeded out by officials of the two main state terror organisations, the JSO and the RDB. The JSO is only 500-strong but they are hand-picked, university educated and highly trained young men known for their extreme violence. The RDB are the plain clothes, Gestapo-style bureaucrats, who have compiled thousands of names of whom the state wishes to "disappear". They are known for their clipboards and ankle-length leather coats.

Large towns such as Mitrovica, Orahovac and Podujevo were almost totally Albanian, so they were largely razed to the ground.

The initial movement of population was into the south-western corner of Kosovo. Prizren, a city only 10 miles from Albania, was cleared out and used as a staging post for Kosovars from as far away as Pristina.

Many villagers tried to flee to former Kosovo Liberation Army strongholds around Malisevo and Orahovac, and areas south of Klina town. But thousands were caught and marched to villages swollen with refugees from earlier Serb offensives.

East of Orahovac, towards Suva Reka, the village of Trnje suffered one of the first outbursts of animal rage, the day after the first Nato air strikes. Refugees say the Serbs rampaged through the village, firing on a group of civilians, many of them women and children, running away. More than 30 were shot dead.

Villagers in the Has region, which straddles the Albanian border, thought that since there had been no fighting in their area, they would be allowed to stay in peace. But by the middle of last week the soldiers showed up and gave them two hours to leave. One village resisted: two hours later the shelling began.

By this time the flow of refugees on the highway south to Macedonia was swelling. It became a flood as the Serbs turned to their final target - Pristina. About 5,000 men of the 24th Special Police Detachment of MUP had been there even before the ethnic cleansing operation had started. In less than two days nearly 90,000 ethnic Albanians had been rounded up. There they were "processed" and those whose names who were on the RDB's clipboards were taken away. For 48 hours the sound of gunfire was heard throughout the city. Then, all Albanian homes and businesses were looted and burned.

On Thursday 20 trains were assembled outside the city. For the next two days the trains made the 50-mile run to the border, each packed with up to 4,000 people. By early yesterday the entire ethnic Albanian population of Pristina seems to have been dumped three miles north of the Macedonian border - causing the huge build-up of refugees now filling an entire valley.

The Serbian Army's entire operation had taken just over a week. "Not even the Nazis did things at this speed," said a Nato source in Skopje. "In just over a week they have cleared an entire region, and by the middle of next week they will probably have rounded up and decanted almost one million men, women and children, from their homeland. How many they have killed, perhaps we will never know."