Resolution 660 condemned the invasion of Kuwait and resolution 678 authorised all necessary means

Background

United Nations Peacekeeping records that on 2 August 1990 Iraq invaded and occupied Kuwait, and that on the same day the Security Council adopted resolution 660 (1990), condemning the invasion and demanding Iraq's immediate and unconditional withdrawal.
A few days later the Council instituted mandatory arms and economic sanctions against Iraq.
Between 2 August and 29 November 1990 the Council adopted twelve resolutions on the situation between Iraq and Kuwait, culminating in resolution 678 (1990).
That resolution specified that if Iraq had not implemented the Council's resolutions by 15 January 1991, Member States cooperating with Kuwait's legitimate Government were authorised to use all necessary means to compel it to do so.
The deadline passed, and on 16 January 1991 the armed forces of the cooperating States began air attacks against Iraq, followed by a ground offensive on 24 February.
Offensive operations were suspended as of midnight on 28 February 1991, by which time Kuwait City had been liberated and all Iraqi armed forces had left Kuwaiti territory.