On 10 June 1999 the UN Security Council issued Resolution 1244, which called for an immediate and verifiable end to violence and repression in Kosovo and for a complete verifiable phased withdrawal of all military, police and para-military forces. This withdrawal would be synchronised with the deployment of an international security presence in Kosovo. The resolution also established the responsibilities of both an international security presence – which was called Kosovo Force (KFOR) – and an international civil presence. The latter was eventually formed as the UN Mission in Kosovo (UNMIK), as the leading international body tasked to provide an interim administration for Kosovo "while establishing and overseeing the development of provisional democratic self-governing institutions to ensure conditions for a peaceful and normal life for all inhabitants of Kosovo." The NATO operation calling for the deployment of KFOR was named "Joint Guardian."
KFOR, which operated under CINCSOUTH as the Joint Force Commander, entered Kosovo on June 12, 1999. Two days later it established tactical command in Pristina, while troops deployed to assigned sectors.
On 20 June 1999, after all FRY military and police forces (VJ/MUP) had departed Kosovo in compliance with the Military Technical Agreement (MTA), NATO's Secretary General decided to terminate the air campaign. Part of the aircraft deployed to conduct Allied Force were eventually authorised to return to home bases. The following day the former Kosovo Liberation Army (KLA/UCK) pledged with another agreement, called the UCK Undertaking, to progressively demilitarise its forces.
The basic mission assigned to NATO Operation "Joint Guardian" was:
- To establish a security presence in Kosovo, as authorised by the United Nations Security Council Resolution 1244 and further defined in the MTA signed by military authorities from the Federal Republic of Yugoslavia and NATO.
- To verify and enforce the terms of the MTA.
- To establish a secure environment in which refugees and displaced persons can return home in safety.
- To establish a secure environment in which the international civil presence can operate, a transitional administration can be established and humanitarian aid can be delivered.
- To help achieve a self-sustaining secure environment which will allow public security responsibilities to be transferred to appropriate civil organisations.
On 8 October 1999 the ARRC was relieved as the core element of KFOR Headquarters by Headquarters Allied Land Forces Central Europe. At that time, there were over 42,000 troops from 27 nations deployed in Kosovo. Together with this change of command, AFSOUTH ceased to be Joint Force Command for KFOR, which reported directly to Allied Command Europe. AFSOUTH, however, did not relinquish all its responsibilities towards KFOR, since it remained a direct support commander with reference to air and maritime power. The same role it had been playing with reference to the NATO-led Stabilisation Force in Bosnia-Herzegovina, SFOR