sentences:  The United States responded to the 11 September 2001 attacks by launching a "Global War on Terrorism", invading Afghanistan to depose the Taliban, who had harbored al-Qaeda terrorists, and enacting the Patriot Act.Many other countries also strengthened their anti-terrorism legislation and expanded law enforcement powers.The 'Global War on Terrorism' is the military, political, legal and ideological conflict against Islamic terrorism and Islamic militants since the 2001 attacks.