On October 23, around 6:20 AM, a yellow Mercedes delivery truck drove to Beirut International Airport, where the United States Marines had their headquarters. It turned onto an access road leading to the compound and circled a parking lot. The driver gunned his engine, crashed through a barbed-wire fence in the compound parking lot, passed between two sentry posts, crashed through a gate, and barreled into the lobby of the Marine headquarters building. The Marine sentries had not had loaded weapons, and were not able to shoot the driver. According to one Marine, the driver was smiling as he sped past him.
The suicide bomber detonated his truck, which contained 12,000 pounds of TNT. The force of the explosion collapsed the four-story cinder-block building into rubble, crushing to death many inside. The FBI later conlcuded that the blast was the largest non-nuclear explosion they had ever seen.
About two minutes later, an identical attack occurred on the French Paratrooper barracks. A truck bomb drove down a ramp into the building's underground parking garage and exploded, leveling the headquarters.
The death toll was 241 for the Marine Barracks attack: 220 Marines, 18 Navy Personnel, and 3 Army soldiers. 60 Americans were injured. In the attack on the French barracks, 58 paratroopers were killed, and 15 injured.
President Ronald Reagan called the attack a "despicable act" and pledged to stay in Lebanon. Secretary of Defense Caspar Weinberger said there would be no change in the US's Lebanon policy. On October 24 French president Francois Mitterrand visited the French and American bomb sites. It was not official, and he only stayed for a few hours, but he did declare: “We will stay.”
In response to the attacks, France launched an air strike in the Bekaa valley against Iranian Revolutionary Guard positions. President Reagan assembled his national security team to devise a plan of military action, and planned to target was the Sheik Abdullah barracks in Baalbek, Lebanon, which housed Iranian Revolutionary Guards believed to be training Hezbollah fighters. However, Defense Secretary Caspar Weinberger aborted the mission, reportedly because of his concerns that it would harm U.S. relations with other Arab nations. There was no real military response from the United States due to the barracks bombing; however, the US did become invovled in several fights in Lebanon during their stay.
Who caused the bombing is uncertain. Most believe the Hezbollah terrorist group, backed by Iran and Syria is responsible for the two barracks bombings, as well as the April 1983 US Embassy bombing. Several Shiite terrorist group claimed the attacks, and one, the Free Islamic Revolutionary Movement, identified the two suicide bombers as Abu Mazen, 26, and Abu Sijaan, 24.
The attack remains the deadliest terrorist attack on Americans overseas, and today it is the fourth-deadliest terrorist attack ever.
(Description of the attack from the World Almanac, 1985 edition).