In July 1958, Lebanon was threatened by civil war between Maronite Christians and Muslims. Tensions had escalated earlier in 1956 when pro-western President Camille Chamoun, a Christian, did not break diplomatic relations with the Western powers that attacked Egypt during the Suez Crisis, angering Egyptian President Gamal Abdel Nasser. These tensions increased further when Chamoun showed closeness to the Baghdad Pact, which Nasser felt threatened Arab nationalism, and Egypt and Syria then united into the United Arab Republic. Lebanese Sunni Prime Minister Rashid Karami supported Nasser in 1956 and 1958, and after the crisis ended he formed a national reconciliation government. Lebanese Muslims pushed the government to join the newly created United Arab Republic, while Christians wanted to keep Lebanon aligned with Western powers. A Muslim rebellion allegedly supplied with arms by the United Arab Republic through Syria led Chamoun to complain to the United Nations Security Council, but United Nations inspectors reported that they found no evidence of significant intervention from the United Arab Republic. Soviet Premier Nikita Khrushchev threatened to use nuclear weapons in the event of American intervention, but President Eisenhower authorized Operation Blue Bat on July 15, 1958, the first application of the Eisenhower Doctrine, under which the U.S. would intervene to protect regimes it considered threatened by international communism. The operation aimed to bolster Chamoun's pro-Western government against internal opposition and threats from Syria and Egypt by occupying and securing Beirut International Airport, then securing the port of Beirut and the approaches to the city. It involved approximately 14,000 men, including 8,509 United States Army personnel, a contingent from the 1st Airborne Group, 187th Infantry from the 24th Infantry Division based in Germany, and 5,670 officers and men of the United States Marine Corps in the 2nd Provisional Marine Force of Battalion Landing Teams 1/8 and 2/2, supported by a fleet of 70 ships and 40,000 sailors. On July 16, 1958, Admiral James L. Holloway, Jr., CINENELM and CINCSPECCOMME, flew in from London to Beirut airport and boarded the USS Taconic (AGC-17), from which he commanded the remainder of the operation. The U.S. withdrew its forces on October 25, 1958.