Terrorism in the United States refers to violent acts intended to intimidate or coerce a population or government. It can be domestic, involving individuals or groups within the country, or international, involving foreign entities. Notable incidents include the September 11 attacks in 2001, which were carried out by the terrorist group al-Qaeda, and the Oklahoma City bombing in 1995, executed by domestic extremists. The U.S. government has implemented various measures to combat terrorism, including the establishment of the Department of Homeland Security and the Patriot Act. These efforts aim to enhance national security and prevent future attacks while balancing civil liberties.