Lebanon had spent the previous few years threatened by a civil war between the Maronite Christians and the Muslims who were its two major religious divisions. As a rule, the Maronites were aligned with the West, and the Muslims with Egypt under Gamel Nasser. Relations with Egypt and Syria had grown tense, further exacerbating the situation.
Finally, the toppling of Iraq’s pro-Western government on July 14 provoked President Chamoun’s call for U.S. assistance. President Eisenhower responded with Operation Blue Bat, commencing on July 15, and ultimately lasting until October 25, 1958. In that time, US forces quelled dissent and helped to stabilise the government. At the time, it was considered a great success, but there are always unintended consequences: in historical terms, however, it can be seen as one more resentment spurring Muslim extremism against the US.
We Didn’t Start The Fire – Billy Joel