On 1 November 1990, Howe, by then the last remaining member of Thatcher's original 1979 cabinet, resigned from his position as Deputy Prime Minister, ostensibly over her open hostility to moves towards European Monetary Union.
In the First multi-party election in Bosnia and Herzegovina, in November 1990, votes were cast largely according to ethnicity, leading to the success of the Bosniak Party of Democratic Action, the Serbian Democratic Party and the Croatian Democratic Union.
The collapse of the Warsaw Pact in 1989–1991 removed the de facto main adversary of NATO and caused a strategic re-evaluation of NATO's purpose, nature, tasks, and focus on the continent of Europe. This shift started with the 1990 signing in Paris of the Treaty on Conventional Armed Forces in Europe between NATO and the Soviet Union, which mandated specific military reductions across the continent that continued after the dissolution of the Soviet Union in December 1991.
On 14 November, Michael Heseltine mounted a challenge for the leadership of the Conservative Party. Opinion polls had indicated that he would give the Conservatives a national lead over Labour. Although Thatcher led on the first ballot with the votes of 204 Conservative MPs (54.8%) to 152 votes (40.9%) for Heseltine and 16 abstentions, she was four votes short of the required 15% majority. A second ballot was therefore necessary. Thatcher initially declared her intention to "fight on and fight to win" the second ballot, but consultation with her Cabinet persuaded her to withdraw. After holding an audience with the Queen, calling other world leaders, and making one final Commons speech, on 28 November she left Downing Street in tears. She reportedly regarded her ousting as a betrayal. Her resignation was a shock to many outside Britain, with such foreign observers as Henry Kissinger and Gorbachev expressing private consternation.
A series of UN Security Council resolutions and Arab League resolutions were passed regarding Iraq's invasion of Kuwait. One of the most important was Resolution 678, passed on 29 November 1990, which gave Iraq a withdrawal deadline until 15 January 1991, and authorized "all necessary means to uphold and implement Resolution 660", and a diplomatic formulation authorizing the use of force if Iraq failed to comply.