Suspicion quickly fell on al-Qaeda, and in 2004, the group’s leader Osama bin Laden, who had initially denied involvement, claimed responsibility for the attacks. Al-Qaeda and bin Laden cited U.S. support of Israel, the presence of U.S. troops in Saudi Arabia, and sanctions against Iraq as motives for the attacks. The United States responded to the attacks by launching the War on Terror, invadingAfghanistan to depose the Taliban, who had harbored al-Qaeda members. Many countries strengthened their anti-terrorism legislation and expanded law enforcement powers. In May 2011, after years at large, bin Laden was found and killed.