allies argued that the invasion was an act of self defense, which is legal according to Article 51 of the Charter of the United Nations. The US sent a letter to the Security Council on October 7 stating that, "Afghanistan was harboring terrorists who attacked the United States, that further attacks might be anticipated, and that military action was needed to deter them." Legal scholar John Quigley has argued that the invasion was illegal because al-Qaeda, not Afghanistan, was the perpetrator of the 9/11 attacks, and because there was no evidence that further terrorist attacks were imminent. Sean Murphy made the opposite case, that Afghanistan was responsible for the actions of al-Qaeda because it allowed al-Qaeda to operate from its territory and refused to extradite al-Qaeda operatives. The debate continued with the 2009 publication of Myra Williamson’s Terrorism, War and International Law: The Legality of the Use of Force Against Afghanistan in 2001. Williamson analyzed the legal questions raised by state responses to terrorism and the implications of the Afghanistan precedent for later conflicts such as the 2003 United States invasion of Iraq and the 2006 Israeli invasion of Lebanon. Reactions and aftermath In October 2001 when the invasion began, polls indicated that about 88% of Americans and about 65% of Britons backed military action. An Ipsos-Reid poll conducted between November and December 2001 showed that majorities in Canada (66%), France (60%), Germany (60%), Italy (58%), and the UK (65%) approved of US airstrikes while majorities in Argentina (77%), China (52%), South Korea (50%), Spain (52%), and Turkey (70%) opposed them. There were a number of protests against the invasion, including 20,000 people in Washington, D.C. on September 29 and 20,000 people in London on October 7. In Afghanistan, according to anthropologist Thomas Barfield, there was "a surprising level of popular support...for the US intervention, especially among non-Pashtuns." In November 2001, CNN reported widespread relief amongst Kabul's residents after the Taliban fled the city, with young men shaving off their beards and women taking off their burqas. On December 20, 2001, the United Nations authorized an International Security Assistance Force (ISAF), with a mandate to help the Afghans maintain security in Kabul and surrounding areas. For its first years ISAF consisted of 8,000 American and 5,000 coalition soldiers and its mandate did not extend beyond the Kabul area. In February 2002, the US detected a large concentration of Taliban and