Hezbollah, which was founded by Lebanese clerics in 1982, has two wings.
One is political and social, and its vibrant political party holds nine seats in the Lebanese Parliament.
The other wing is a guerrilla military force. The United States put Hezbollah on its terrorist list in 1997.
Unlike al-Qaida, Hezbollah has never targeted Americans on U.S. soil. But its operatives have killed nearly 300 Americans overseas in the last 20 years, including 241 service members in a Marine barracks in Beirut, Lebanon.