From the late 1990s to the early 2000s, international interventions authorized by the UN took a wider variety of forms. United Nations Security Council Resolution 1244 authorised the NATO-led Kosovo Force beginning in 1999. The UN mission (1999-2006) in the Sierra Leone Civil War was supplemented by a British military intervention. The invasion of Afghanistan in 2001 was overseen by NATO. In 2003, the United States invaded Iraq despite failing to pass a UN Security Council resolution for authorization, prompting a new round of questioning of the organization's effectiveness.