The destruction of the World Trade Center and a wing of the Pentagon by three highjacked civilian airliners and the crash of a fourth in Pennsylvania on September 11, 2001 constitute without a doubt the high point of terrorist attacks on the United States to date. The terrorists’ methods, their destructive force and the attacks’ economic and political effects are all without precedent. After September 11, the organisation responsible was quickly identified, namely a terrorist group based in Afghanistan, Al Qaeda, headed by a Saudi expatriate, Osama bin Laden. After a request for his extradition was denied by the ruling Taliban, the United States and the United Kingdom conducted airstrikes against targets in Afghanistan beginning on October 7. As soon as late November 2001, the Taliban's fate was sealed. The uninterrupted bombardment of the US Air Force helped the Northern Alliance gain decisive ground in its campaign against the regime. On December 15, 2001, the various Afghan opposition groups signed a treaty on the Petersberg near Bonn, Germany, that established an interim government. The government's establishment put an end to the Taliban's rule, but it did not put an end to international terrorism with its various goals and interwoven structures.