On October 23, 1983, a suicide bomber drove a truck packed with explosives into the United States Marine barracks in Beirut, Lebanon, according to History.com and the Naval History and Heritage Command.

The blast killed 241 American military personnel, the sources say. They included Marines, sailors and soldiers, History.com and the Navy command say.

That same morning, a second suicide bomber hit a building housing French troops two miles away, History.com says. The attack killed 58 French soldiers, it says.

The troops were part of a multinational peacekeeping force in Lebanon, the sources say. Lebanon was in the middle of a civil war, they note.

United States Marines were first sent to Beirut in August 1982, History.com says. They helped oversee the Palestinian withdrawal from the city, it says.

The bomber drove his truck through three guard posts and a barbed-wire fence, History.com says. He set off the bomb in the lobby of the Marine headquarters, it says.

The Navy command says it was the deadliest single day for the Marines since the first day of the assault on Iwo Jima.

The Navy command says the Islamic Jihad Organization carried out the attacks, with funding and training from Iran's Revolutionary Guard Corps. History.com says the bombers were suspected to be Shiite militants linked to Iran.

Earlier that year, in April, a suicide bomber hit the American embassy in Beirut, History.com says. That attack killed 63 people, including 17 Americans, it says.

President Ronald Reagan first vowed to keep the Marines in Lebanon, History.com says. Four months later, he ended the American role in the force, it says.

The main force of Marines left Lebanon on February 26, 1984, History.com says.

What we know: The 1983 bombing killed 241 American service members and 58 French soldiers.
What we don't: Exactly who planned the attacks, which is still debated.