The Allied attack on Afghanistan began in October 2001, and, following the fall of the Taliban, a US Justice Department dossier on Begg alleges that he joined their retreat to the Tora Bora mountains. The Pentagon claims that he was "prepared to fight in the front line against allied forces". He says that he and his family intended to evacuate to Islamabad in Pakistan for safety. Initially he became separated from his family in Afghanistan, he and several other men were guided over the mountains into western Pakistan, and he was reunited with his family in Pakistan by mid-November.