In 1998, open military conflict escalated in Kosovo. On 28 May 1998, the North Atlantic Council stated NATO's major aims in regard to Kosovo: to achieve a peaceful resolution to the crisis by contributing to the response of the international community and to promote stability and security in neighbouring countries with particular emphasis on Albania and the former Yugoslav Republic of Macedonia (document no. 152). On 11 June 1998, the North Atlantic Council asked for an assessment of possible further measures that NATO might take considering the developing crisis (document no. 153). This led to a consideration of a large number of military options.

On 24 September 1998, NATO first decided to have recourse to a threat to use force in order to resolve the Kosovo conflict and issued an Activation Warning for both a limited air operation and a phased air campaign (document no. 154). In autumn 1998, the approaching winter with the threat of a humanitarian catastrophe among the internally displaced people caused the international community to demand a ceasefire. On 8 October 1998, the Contact Group decided to send US Special Envoy Richard Holbrooke to Belgrade “with the full authority of the Contact Group” to demand compliance with UN Security Council Resolution 1199 (1998). His mission was accompanied by a renewed military threat by NATO and by Russian approval of an OSCE verification mission on the ground. This combination caused Milosevic to accept the Contact Group's mediation and negotiate with Holbrooke.