The 1958 Civil War was instigated by Lebanese Muslims and Druzes who were inspired by the February 1958 unification of Egypt and Syria and agitated to make Lebanon a member of the new United Arab Republic. Pro-Nasser demonstrations grew in number and in violence until a full-scale rebellion was underway. The unrest was intensified by the assassination of Nassib Matni, the Maronite anti-Shamun editor of At Talagraph, a daily newspaper known for its outspoken pan-Arabism . The revolt almost became a religious conflict between Christians and Muslims.
This state of turmoil increased when, in the early hours of July 14, 1958, a revolution overthrew the monarchy in Iraq and the entire royal family was killed. In Lebanon jubilation prevailed in areas where anti-Shamun sentiment predominated, with radio stations announcing that the Shamun regime would be next. Shamun, realizing the gravity of his situation, summoned the ambassadors of the United States, Britain, and France on the morning of July 14. He requested immediate assistance, insisting that the independence of Lebanon was in jeopardy.
Although the war took a toll of some 2,000 to 4,000 lives, it was regarded by many as a comic opera, especially when 5,000 United States Marines were landed on the beaches near Beirut and waded ashore among sunbathers and swimmers. The Marines' role, in a situation described by the Department of Defense as "like war but not war," was to support the legal Lebanese government against any foreign invasion, specifically against Syria. The Marines were summoned because Shihab, believing that the army would mutiny and disintegrate if ordered into action, had disobeyed President Shamun's orders to send the army against Muslim rebels. Thus, Lebanon's army had once more proved unwilling to defend Lebanon's government.
Nevertheless, Shihab's reputation for even-handedness was enhanced by his refusal to commit the army to ending the Civil War, and he succeeded Shamun as president. Shihab pictured himself as a military statesman like Charles de Gaulle. Although he relied heavily on the Deuxième Bureau (the military intelligence branch of the army), as his power base, he surrendered command of the Lebanese Army and did not rule as a military dictator. On the contrary, he was a reformer who made significant concessions to Muslims in an attempt to heal the wounds of the 1958 Civil War.