Terrorist attacks can happen on an international or domestic scale. International terrorism is defined as “violent, criminal acts committed by individuals and/or groups who are inspired by, or associated with, designated foreign terrorist organizations or nations (state-sponsored),” according to FBI.gov.

Domestic terrorism is defined as “violent, criminal acts committed by individuals and/or groups to further ideological goals stemming from domestic influences, such as those of a political, religious, social, racial, or environmental nature,” per the source. TheFederal Bureau of Investigation (FBI) is the primary agency that is responsible for both investigating and preventing terrorism on an international and domestic level.

Al-Qaeda, ISIS, Hamas and the Taliban are all examples of groups the U.S. government has named foreign terrorist organizations.

A tragic day in American history occurred onSeptember 11, 2001, when the Twin Towers in New York City collapsed after being struck by commercial airplanes. A plane also crashed into the Pentagon, and a fourth crashed in Pennsylvania. This terrorist attack was orchestrated by Al-Qaeda, which was led by Osama bin Laden. Bin Laden was killed by Navy SEALs in May 2011 when Barack Obama was Commander-in-Chief.