On September 20, 1984, a van loaded with several hundred pounds of explosives drove through the gates of the American embassy annex in the Christian suburb of Ain el-Mraisseh in east Beirut and detonated against the building. Twenty-three people were killed, including the two American servicemen on guard and 21 Lebanese staff and visitors, and about 60 were wounded. Islamic Jihad claimed it.
It was the third attack. In April 1983 a bomb at the embassy itself killed 63 people. In October 1983 a truck bomb at the marine barracks at Beirut airport killed 241 Americans and 58 French paratroopers in two simultaneous attacks. The Americans had come in as part of a multinational force in September 1982, after the Israeli invasion and the Sabra and Shatila massacre, and had been drawn into supporting the Lebanese government against its own population.
By 1984 they were leaving. The marines had been withdrawn to ships in February after the airport bombing, and the embassy had been consolidated into the annex, a six-storey building with a Marine guard detachment and a CIA station. The guard had been trained to fire at vehicles approaching at speed, and the checkpoint had been moved a few days before the attack, which is what let the van get close enough to do the damage it did.
The attacker was never identified with certainty, and the claim of responsibility was one of many that Islamic Jihad and Hezbollah made and that were impossible to verify. What is known is that the bombing was part of a campaign: Westerners in Beirut were kidnapped from 1982 onward, and about 100 foreign hostages were taken, of whom 25 were American, and eight died or were killed in captivity.
The American withdrawal was complete by 1985 and the embassy was closed. It reopened in Beirut in 1990, after the civil war, in a new compound. The hostage crisis ended in 1991 with the release of the last American hostages, and it produced the Iran-Contra affair, in which the Reagan administration had sold arms to Iran in the hope of getting hostages freed and had used the money to fund the contras in Nicaragua.