On 15 July 1958, President Dwight Eisenhower authorized military intervention in Lebanon under the codename Operation BLUE BAT. Over the next three months, challenged by intelligence gaps, members of the U.S. Navy, Marine Corps, and Army occupied the Port of Beirut and the Beirut International Airport as peace-keeping entities.

After the Suez Crisis in 1956—wherein Israel, followed by the United Kingdom and France, invaded Egypt to retake control of the Suez Canal Zone—a marked increase was visible in hostilities between Arabs in northern Africa and the Middle East and the West. The resulting decrease in foreign aid from the West led Egyptian Prime Minister Gamal Abdul Nasser to accept economic and political aid from the Soviet Union. This, in turn, provoked the U.S. to view Egypt as another proxy nation through which the Soviet Union could spread communism. In early 1957, Congress approved the Eisenhower Doctrine to provide economic and military aid to contain communism within “at-risk” Middle Eastern nations.

Lebanon’s President Camille Chamoun, a Christian Maronite and staunch anti-communist, was the only one to accept American aid. However, the growing pro-Nasser, Arab nationalist factions strongly opposed Western interference in the region. In the lead-up to the Lebanese parliamentary elections in the summer of 1957, disputes between these camps erupted in Beirut and nearby cities. The Lebanese Army was called in to help quell the violence. However, given the army’s divided loyalties, the soldiers refused to take sides in the conflict and instead acted “as a passive sort of constabulary.” On 8 May, a Christian critic of Chamoun named Nasib Metni was assassinated, sparking immediate riots throughout the country. These soon intensified into a civil war.

President Chamoun called on the United States to send military aid to restore order in Beirut. On 15 July 1958, Eisenhower agreed to send military forces and, the next day, the 2d Provisional Marine Force (Task Force 62) landed on the beaches of Beirut as the initial neutralizing force. Expected to be a conventional military intervention, the operation quickly proved far more complicated. Significantly, Lebanon had not been an American intelligence priority in the 1950s, and in May 1958, protestors had ransacked the U.S. Information Service Library in the U.S. Embassy, making it difficult for embassy staff to report timely and accurate information to government officials planning the intervention. Consequently, Marines landing in Lebanon had little understanding of the conflict’s nature or of the city’s geography, as they were supplied with maps drawn by the French during World War II.

Furthermore, the U.S. Army misunderstood the political and social landscape of the region. Prior to the arrival of members of the 1st Airborne Battle Group, 187th Infantry, 24th Infantry Division, Brig. Gen. David Gray instructed Force Alpha, one of five unit “forces” assigned to Army Task Force 201, that “communists were responsible for the troubles besetting Lebanon.” In late July, when the Army began relieving the Marines in Beirut, the U.S. finally realized the crisis was primarily caused by smaller political groups throughout the city and had little to do with the spread of communism in the country.

The Army found the best sources of intelligence within the National Union Front, an anti-Chamoun, Arab nationalist organization, and the “Parti Populaire Syrien”, an illegal pro-government group. Intelligence officers quickly determined that effectively quelling the violence in Lebanon did not require military force but instead a demilitarization of these two groups. The Army’s intelligence helped reshape the objective of American intervention in Beirut in late 1958, allowing the Army to successfully oversee the Lebanese election that ousted Chamoun from office on 25 October.