It was the alliance's first intervention against a sovereign state in its 50-year history.

Thirteen months earlier, Milosevic had deployed troops into Kosovo, then still a Serbian province, whose population was 90 percent ethnic Albanian. He was trying to crush the pro-independent Kosovo Liberation Army (KLA) guerrillas.

Some 13,000 people, mostly Albanian, were killed and around one million driven from their homes during the two-year conflict.

- Diplomacy fails -

Milosevic had steadfastly refused over February and March 1999 to accept a peace accord hammered out at Rambouillet chateau near Paris which provided autonomy for the province.

NATO members feared the conflict would spread throughout the Balkans, only three years after the end of wars in the former Yugoslav republics of Bosnia and Croatia.

An 11th-hour visit by US envoy Richard Holbrooke to Belgrade to try to mediate the crisis failed to budge Milosevic.

- NATO orders strikes -

NATO headquarters gave the go-ahead for air strikes late on March 23, saying the decision was taken in agreement with all 19 of its members.

Every attempt to find a negotiated political solution had failed, said Secretary General Javier Solana: "There is no alternative but to take military action."

The first bombs fell a day later, with strikes around 8:00 pm on Belgrade, Kosovo's capital Pristina and other cities and towns.

Serbia television aired dramatic pictures of buildings engulfed in flames, smoke billowing high into the night sky.

The attacks were carried out without a green light from the United Nations, where Serbia's ally Russia, and China, were against military intervention.

- Preventing 'catastrophe' -

US president Bill Clinton went live on television to say the NATO strikes were vital to prevent the Kosovo "powder keg" from triggering a bigger conflict.

"We act to prevent a wider war, to defuse a powder keg at the heart of Europe, that has exploded twice before in this century with catastrophic results," he said.

British said eight NATO member states had taken part in the opening wave of attacks -- Britain, Canada, France, Germany, Italy, the Netherlands, Spain and the United States.

Some 70 aircraft, including 10 F-117 Stealth bombers, took off from a NATO air base in northern Italy in successive waves, spokesmen said.

- Ethnic cleansing -

NATO appeared confident that a few days of "surgical" air strikes would bring Milosevic back into negotiations.

Instead the Yugoslav leader stepped up his brutal campaign against the province's ethnic Albanian community.

The world watched in horror as hundreds of thousands of Albanians were driven from their homes.

As refugees began to arrive in neighbouring Albania and Macedonia, tales emerged of homes being burned out, summary executions and mass rapes.

- Civilians killed -

Over the 11-week campaign NATO aircraft carried out 38,000 sorties, including 10,000 bombardments, according to alliance figures.

Attacks were extended beyond purely military targets to include key infrastructure such as petroleum and power plants, road and rail bridges and, most controversially, the installations of Serb television and radio.

Blunders such as the bombing of the Chinese embassy in Belgrade or the attack on a refugee convoy near Djakovica severely tested the allies' commitment to the campaign.

- Milosevic capitulates -

The civilian death toll has never been established: 500, according to NGO Human Rights Watch; 2,500 according to the Serbian authorities.

Milosevic had to contend with the losses of his soldiers, hints of a rebellion among his generals, a crippled economy and no sign of a let-up in the NATO bombing.

On June 10, 1999 he finally ordered his forces to withdraw from Kosovo, which was effectively taken over by the international community.

Kosovo declared independence in 2008, a move Serbia, China and Russia refuse to recognise.