The details of Operation Joint Guardian are being finalised, but the principles were agreed at a "special force generation conference" on 1 June, when 30 countries - the 19 Nato members and 11 "partners for peace" - pledged a total of 47,868 troops for K-For, the new peacekeeping force in the Balkans.

K-For will operate under United Nations auspices but will remain under Nato military command.

Serb withdrawal

Yugoslavia's withdrawal is the critical first stage of "sequencing" the arrival of K-For and the return of refugees.

Lt Gen Sir Mike Jackson: Head of Nato's Kosovo ground forces

After days of protracted talks in Kumanovo, Macedonia, Yugoslav forces have agreed a strict 11 day withdrawal schedule from three zones running south to north.

As Yugoslav forces leave through the four "secure exit points", K-For will take control of area after area.

Nato will monitor and verify the withdrawal through air reconnaissance and media reports.

Yugoslav and Serb forces are expected to be outside the province by the end of day 11 and Nato will establish a 5km buffer zone inside Serbia.

Nato says it will only accept a token Yugoslav presence in the province to protect sites of historic or cultural importance.

Contingents

The peacekeeping force of 48,000 is the largest yet to be deployed to the Balkans.

Click here for a map showing how K-For will enter Kosovo.

Around 13,000 UK troops are arriving in the Balkans and another 6,000 are on stand-by, making it the largest single force.

Units include members of the Paratroop regiment, the Irish Guards and the Gurkhas.

The US is providing 7,000 troops including an expeditionary unit of 2,000 Marines which landed in northern Greece on Thursday morning local time.

Germany is currently providing a quarter of all Nato troops in Macedonia and Albania. It will be sending 8,000 troops into the province.

France and Italy are contributing an additional 7,000 and 5,000 respectively.

The Netherlands are sending 2,050 troops, Spain 1,200, Belgium 1,100 and Greece 1,000.

Turkey and Norway are sending around 1,000 each, Denmark 850, Poland 800 and Canada 800.

Numbers committed to the force by Russia remain unclear. Nato leaders suggest that Moscow cannot afford to send more than a few thousand troops at best.

But Russian defence minister Igor Sergeyev the Kremlin is preparing to send between 2,000 and 10,000 troops.

Other nations are supplying smaller numbers of troops or support staff.

Deployment

The majority of the troops will enter the province through Macedonia within hours of a verified Serb withdrawal beginning to prevent the Kosovo Liberation Army taking positions.

Nato spokesman Jamie Shea said: "We are not going to wait until the last Serb soldier has gone and turned off the light.

"There will be no vacuum, just a little gap between the last boot of the Serb forces and the first boot of Nato's troops."

Mine clearance specialists will liaise with Yugoslav forces to remove explosives planted along the border.

The most difficult point of entry is the Kacanik pass between the province and the Macedonian border town of Blace.

This 12km ravine with two tunnels and 14 bridges is believed to be heavily mined and clearance specialists will be under pressure to declare it safe within hours.

The mine specialists will be followed by more than 1,000 vehicles from heavy armoured divisions, including UK Challenger tanks, US armoured forward vehicles and, in the air, Apache attack helicopters.

Airborne divisions led by British Paratroopers are expected to be sent straight to Pristina, the provincial capital.

Once they hold key command positions, signals units, medical teams and other logistical support units follow.

K-For's commander, Lieutenant-General Sir Mike Jackson, has ordered his forces to exercise "even-handedness" towards both Yugoslav and Kosovo Liberation Army forces.

Sectors

This remains the bone of contention between Russia and Nato.

The five leading Nato members, the US, UK, France, Germany and Italy, will each administer a "sector" of the province in arrangements similar to the S-For command structure in Bosnia.

The UK, the largest force, will command K-For headquarters at Pristina airport.

Italy will control the Pec sector in the west while the USA will take the Grijilane sector bordering Macedonia.

German troops will operate in the south-west around Prizren and France will command the northern border regions with Serbia.

The exact role of Russia remains unclear.

Russia has demanded its own non-Nato sector - with suggestions that it would want control of the north-east.

But US Secretary of State Madeleine Albright said: "Nato will be embedded in every sector," indicating the alliance's determination to stick to a single command structure.

The UK's foreign secretary Robin Cook said that there would be no "East Germany" within Kosovo, ruling out a de facto partitioning of Kosovo.

Humanitarian concerns

While K-For will seek military control, troops must create safe conditions for the race to deliver humanitarian aid.

Thousands of Kosovo Albanians are believed internally displaced and aid agencies want swift access to these groups, many of which are expected to be suffering from malnutrition and the effects of living in the open.

Nato has created two-hour windows at dawn in recent days for aid drops to areas where refugees are believed to be sheltering.

At the same time, the peace implementation force will need to begin the immediate reconstruction of homes, roads, bridges, communications systems and the province's electricity supplies to provide a basic living environment for returning refugees.

War crimes

The International Criminal Tribunal has pledged to send in investigators as soon as it is safe to do so.

But there are fears that the delays in implementing Operation Joint Guardian has provided enough time for potential evidence of war crimes to be destroyed.

One report in the Observer newspaper suggested that Serb units had already used a mine in the north of the province to allegedly dispose of the bodies of Kosovo Albanian men.

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