On 10 June 1999, the UN Security Council adopted a detailed resolution that outlined the civil administration and peacekeeping responsibilities in Kosovo and paved the way for peaceful settlement of the conflict and the safe return home of hundreds of thousands of Kosovo Albanian refugees and displaced persons. The resolution was passed under Chapter VII of the UN Charter which allowed the security forces to carry weapons to protect themselves and use force in carrying out the resolution's directives. The resolution "authorizes member states and relevant international organizations to establish the international security presence in Kosovo" as set out in the military agreement between NATO and the FRY. That peacekeeping operation was meant to enforce the cease-fire, demilitarize the KLA and other Kosovo Albanian groups, and establish a secure environment for the return of the refugees.

The force had a unified NATO chain of command under the political direction of the North Atlantic Council in consultation with non-NATO force contributors. The NATO countries were united that in the absence of the NATO Joint Guardian force at the core of any international security presence in Kosovo, the refugees would not return and the other NATO objectives would not be met. A NATO force at the core of an international security presence was regarded as the magnet to attract the refugees back. In the absence of a NATO force with American participation, it was the view of the US Government that it was unrealistic to think the Kosovar Albanians would disarm the KLA, something of great interest to Russia. The US believed that if NATO forces deployed, the rationale for the Kosovar Liberation Army having an armed force to protect itself against Serbs would disappear. The Rambouillet envisaged something like 2,500 Serb military and 2,500 police for a year, though with the commencement of Operation Allied Force NATO required all of those forces going, in views of the probability that the Kosovar Albanians would not come home to a situation where those same forces remain at their posts. NATO envisaged the standing up of thousands of Kosovar Albanian police, including possibly people from the KLA, who would be trained by the international community and could serve police functions.

NATO did not contemplate a partition of Kosovo. It had been unofficially suggested that one possible solution was a de facto partition of Kosovo whereby the Russians would patrol the north, the mineral-rich areas, and NATO would patrol the south.

Before Allied Force began operating, NATO had plans to put in a peacekeeping force of 28,000 people. Of that, 4,000 people would have been Americans. By mid-May 1999 NATO had reassessed its Op Plan for the Joint Guardian mission to see to what degree they would need reinforcement beyond the level that was originally foreseen for the KFOR [Kosovo force] international security presence in Kosovo. NATO had 16,000 troops deployed in the former Yugoslav Republic of Macedonia trained for their mission as well as dealing with the enormous refugee inflow. Certain reinforcements from the UK and from Germany were arrived as of mid-May.

The NATO pre-deployment in the former Yugoslav Republic of Macedonia was conducted to be in a position to move very quickly into Kosovo to set up an initial military command structure and an initial infrastructure to get the basic functions going. The goal was not only for other NATO troops to come in quickly but also for the transition authority and for the humanitarian relief organizations, which in the very early stages would need a great deal of military back-up, to establish themselves by the time the NATO core element was on the ground in Kosovo.