The buildup of forces continued, reinforced by United Nations Security Council Resolution 678, which called for Iraqi forces to leave Kuwait. On 17 January 1991, U.S. and coalition forces launched Operation Desert Storm with a massive air interdiction campaign, which prepared the theater for a coalition ground assault. The primary coalition objective, the liberation of Kuwait, was achieved on 27 February, and the next morning a ceasefire was declared, just one hundred hours after the commencement of the ground campaign.