On March 24, 1999, the North Atlantic Treaty Organization (NATO) commences air strikes against Yugoslavia with the bombing of Serbian military positions in the Yugoslav province of Kosovo. The NATO offensive came in response to a new wave of ethnic cleansing launched by Serbian forces against the Kosovar Albanians on March 20.

The Kosovo region lay at the heart of the Serbian empire in the late Middle Ages but was lost to the Ottoman Turks in 1389 following Serbia’s defeat in the Battle of Kosovo. By the time Serbia regained control of Kosovo from Turkey in 1913, there were few Serbs left in a region that had come to be dominated by ethnic Albanians.

In 1918, Kosovo formally became a province of Serbia, and it continued as such after communist leader Josip Broz Tito established the Federal People’s Republic of Yugoslavia in 1945, comprising the Balkan states of Serbia, Croatia, Bosnia-Herzegovina, Montenegro, Slovenia, and Macedonia. However, Tito eventually gave in to Kosovar’s demands for greater autonomy, and after 1974 Kosovo existed as an independent state in all but name.

Serbs came to resent Kosovo’s autonomy, which allowed it to act against Serbian interests, and in 1987 Slobodan Milosevic was elected leader of Serbia’s Communist Party with a promise of restoring Serbian rule to Kosovo.

In 1989, Milosevic became president of Serbia and moved quickly to suppress Kosovo, stripping its autonomy and in 1990 sending troops to disband its government. Meanwhile, Serbian nationalism led to the dissolution of the Yugoslav federation in 1991, and in 1992 the Balkan crisis deteriorated into civil war. A new Yugoslav state, consisting only of Serbia and the small state of Montenegro, was created, and Kosovo began four years of nonviolent resistance to Serbian rule.

The militant Kosovo Liberation Army (KLA) emerged in 1996 and began attacking Serbian police in Kosovo. With arms obtained in Albania, the KLA stepped up its attacks in 1997, prompting a major offensive by Serbian troops against the rebel-held Drenica region in February-March 1998. Dozens of civilians were killed, and enlistment in the KLA increased dramatically.

In July, the KLA launched an offensive across Kosovo, seizing control of nearly half the province before being routed in a Serbian counteroffensive later that summer. The Serbian troops drove thousands of ethnic Albanians from their homes and were accused of massacring Kosovo civilians.

In October, NATO threatened Serbia with air strikes, and Milosevic agreed to allow the return of tens of thousands of refugees. Fighting soon resumed, however, and talks between Kosovar Albanians and Serbs in Rambouillet, France, in February 1999 ended in failure.

On March 18, further peace talks in Paris collapsed after the Serbian delegation refused to sign a deal calling for Kosovo autonomy and the deployment of NATO troops to enforce the agreement. Two days later, the Serbian army launched a new offensive in Kosovo. On March 24, NATO air strikes began.

In addition to Serbian military positions, the NATO air campaign targeted Serbian government buildings and the country’s infrastructure in an effort to destabilize the Milosevic regime. The bombing and continued Serbian offensives drove hundreds of thousands of Kosovar Albanians into neighboring Albania, Macedonia, and Montenegro. Many of these refugees were airlifted to safety in the United States and other NATO nations.

On June 10, the NATO bombardment ended when Serbia agreed to a peace agreement calling for the withdrawal of Serb forces from Kosovo and their replacement by NATO peacekeeping troops.

With the exception of two U.S. pilots killed in a training mission in Albania, no NATO personnel lost their lives in the 78-day operation. There were some mishaps, however, such as miscalculated bombings that led to the deaths of Kosovar Albanian refugees, KLA members, and Serbian civilians. The most controversial incident was the May 7 bombing of the Chinese embassy in Belgrade, which killed three Chinese journalists and caused a diplomatic crisis in U.S.-Chinese relations.

On June 12, NATO forces moved into Kosovo from Macedonia. The same day, Russian troops arrived in the Kosovo capital of Pristina and forced NATO into agreeing to a joint occupation. Despite the presence of peacekeeping troops, the returning Kosovar Albanians retaliated against Kosovo’s Serbian minority, forcing them to flee into Serbia. Under the NATO occupation, Kosovar autonomy was restored, but the province remained officially part of Serbia.

Slobodan Milosevic was ousted from power by a popular revolution in Belgrade in October 2000. He was replaced by the popularly elected Vojislav Kostunica, a moderate Serbian nationalist who promised to reintegrate Serbia into Europe and the world after a decade of isolation.

Slobodan Milosevic died in prison in the Netherlands on March 11, 2006, during his trial for crimes against humanity and genocide. Due to his death, the court returned no verdict.

What Is NATO’s Article 5?

The article, as the cornerstone of a treaty signed in 1949, establishes solidarity among member states and has been invoked only once.

Article 5 is the cornerstone of the North Atlantic Treaty Organization (NATO)  and states that an attack on one member of NATO is an attack on all of its members. Despite its importance, NATO has only invoked Article 5 once in its history—in response to the terrorist attacks of September 11, 2001.

NATO Established After World War II

NATO and Article 5 were established in 1949 in the aftermath of World War II when Communist movements supported by the Soviet Union posed a serious threat to democratically elected governments all over a devastated Europe. In 1948, the Communist Party of Czechoslovakia overthrew that nation’s democratic government, while in Germany, Soviet authorities blockaded the Allied-controlled section of Berlin in an attempt to strengthen their position there.

The Berlin Airlift, when U.S. and British planes carried food, fuel and other vital supplies to the isolated citizens of West Berlin, marked an early victory for the West in the Cold War. And with the launch of the Marshall Plan, which provided economic aid to the war-ravaged countries of Europe, the United States had decisively abandoned its earlier policy of isolationism.

But at such a vulnerable time, it seemed clear that Europe required not just economic aid, but also military support, in order to counterbalance the power of the Soviet Union, prevent the revival of nationalist military movements (such as Nazism) and allow for political development along democratic lines.

The Formation of NATO

Tensions between the United States and the Soviet Union resulted in the formation of key alliances that would endure throughout the Cold War.

In April 1949, representatives from 12 nations—the United States, Canada, Great Britain, France, Belgium, the Netherlands, Norway, Denmark, Luxembourg, Iceland, Italy and Portugal—gathered in Washington, D.C. to sign the North Atlantic Treaty.

“Men with courage and vision can still determine their own destiny,” President Harry S. Truman declared at the signing ceremony. “They can choose slavery or freedom—war or peace…If there is anything certain today, if there is anything inevitable in the future, it is the will of the people of the world for freedom and for peace.”

Article 5 Text: ‘An Attack Against One…’

The treaty’s key provision was Article 5, which began: “The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all…” While this commitment to collective defense lay at the heart of NATO, it was left to the judgment of each member state to decide how exactly it would contribute.