Syria's post-1973 confidence in its military capability contributed to its intervention in the civil war that broke out in Lebanon in 1975. Syrian ties to the area comprising modern-day Lebanon had been close for centuries Lebanon was part of Greater Syria under the Ottoman Empire, and both nations were subject to French Mandate authority between the two world wars (see The French Mandate , ch. 1 Foreign Policy , ch. 4). Thus, Syrian leaders viewed Lebanon's instability as a threat to Syria's internal and external security interests, and Syria considered itself strong enough to impose a military solution on the Lebanese conflict.

In 1975 Syria played a vital diplomatic role throughout the initial stages of the civil war. It acted as mediator for the many cease-fires declared between Lebanon's Christians, who dominated the country politically and economically, and the majority Sunni and Shia (see Glossary) Muslims. The latter sought to transform Lebanon into a Muslim Arab country their drive for greater power was afforded a military option by the presence of thousands of armed Palestinian guerrillas who had relocated in Lebanon after the PLO's 1970-71 defeat in Jordan. It was not until January 1976, however, when a detachment of fifty Syrian officers was sent to Beirut to help police the twenty-sixth cease-fire, that Syrian military personnel entered Lebanon. On March 16, Syria escalated its involvement by ordering Syrianbacked units of the Palestine Liberation Army (PLA, the standing army of the PLO) and As Saiqa to stop rebel leftist Muslim officers of the Lebanese Army from attacking the palace of the country's Christian president, Sulayman Franjiyah (also spelled Frangie, Franjieh, or Franjiye) (see Special and Irregular Armed Forces , this ch.).

Lebanese Muslims and the PLO opposed the Syrian intervention, which had prevented them from seizing the presidency from the Christians. Much of the Arab world was outraged. The Syrian intervention also gave rise to a crisis of allegiance within the PLA and As Saiqa units, which found themselves battling forces closely aligned with the PLO. For their part, Syrian leaders talked of peace and stability in Lebanon, while privately acknowledging that their concept of Syria's own security interests made it necessary to have a moderate Lebanese government compatible with Syrian interests. In their judgment, a radical left-wing Muslim Lebanese government would have been a security risk to the Assad regime, which preferred a Lebanese state subservient to its own regional interests.

Syrian presence in Lebanon grew rapidly. Around 3,000 Syrian regulars crossed Lebanese borders on April 9. In May the Lebanese Parliament elected a new, Syrian-backed, Christian president, Elias Sarkis. By October more than 22,000 Syrian troops had en 15d8 ntered Lebanon. The Syrian presence was sanctioned by the Arab League as the major component of the Arab Deterrent Force (ADF), to which the League gave a mandate to stop any breach of the peace. The ADF was technically under the command of President Sarkis, but de facto power and control were in the hands of Syrian military commanders.

After the June 1978 slaying by rival Christian militiamen of Christian leader Tony Franjiyah, son of the former president and Syria's firmest supporter in Lebanon, the ADF began a campaign against Lebanese Christians that included massive artillery barrages on Christian-held territories in East Beirut and other areas. With this action, Syria in effect "switched sides" in the ongoing civil war. The reason for this switch was the call by Lebanese Christians, whose confidence had been bolstered by increasingly overt Israeli support, for a partition of Lebanon along religious lines. This call constituted the major challenge to Lebanese stability and the authority of the Lebanese government.

The majority of Syrian troops deployed in Lebanon were formed into at least three divisions. Armored brigades and commando units were also present, and naval and air force units were used for transport purposes. Syria's heavy use of artillery, both against Muslim factions in earlier fighting and against Christian factions later, caused widespread criticism that the bombardments were indiscriminately killing civilians and that Syrian troops were pursuing a policy of genocide toward Lebanese Christians.

In 1987 Syria's military presence in Lebanon remained an urgent security issue. In early 1987 the ADF in Lebanon consisted of 25,000 Syrian troops (the troops from Saudi Arabia, Sudan, and the United Arab Emirates had withdrawn). The ADF units were deployed throughout those areas of central and northern Lebanon not under the control of the Christian militias. They were not deployed south of the so-called "red line" at the Litani River, near the Israeli border, or in the area controlled by the Israeli-dominated SLA.

In February 1987, there was an intensification of clashes between militiamen of the Syrian-backed Shia Amal and a coalition of Palestinians, Druzes, and the Lebanese Communist Party. A renewed deployment of an estimated 7,000 Syrian troops in West Beirut and major highways linking Beirut to the mountains and the northbound coastal road from southern Lebanon followed. Lebanese Muslim leaders requested Syrian deployment, which was condemned by some Maronite officials. Under the agreement for the Syrian entry, the militias were to disband their forces and lay down their weapons. To restore order, the Syrian troops, stationed at most intersections, closed down militia offices, confiscated arms caches, and rounded up militia and neighborhood strongmen. There was concern, however, that the Syrians would have difficulty resolving Lebanon's complex set of rivalries and disarming remaining militia strongholds in and around Beirut. For instance, Beirut's southern suburbs remained a stronghold of Shia militants, particularly the growing pro-Iranian Party of God, Hizballah, whose uncontrolled militancy and hostage-taking also had become increasingly troublesome to Damascus. Meanwhile, Christian militiamen still held ground in East Beirut.

In early 1987, few analysts believed Syrian occupation would end until the Lebanese conflict was resolved. In its own security interests, Syria could not afford for either radical leftist or religiously fundamentalist Muslim groups to gain total control of Lebanon. Also, President Assad had invested his political reputation, both at home and within the Arab world, in Syrianimposed solutions to the civil war. Nevertheless, the Syrian intervention was becoming increasingly costly to Syria's economy as well as to the morale of the participating armed forces. Above all, it weakened Syria's military threat to Israel by dividing its forces into two fronts and diverting resources from recapturing the Golan Heights at the same time, the intervention increased the possibility of direct confrontation with Israel. In early 1987, following the Israeli withdrawal to south Lebanon, the Syrian order of battle in Lebanon was reported to consist of about two divisions, with a deployment of some six divisions along the Damascus-Golan Heights region.

Some experts believed Syrian leaders preferred to maintain the chaotic situation in Lebanon to preserve Syria's hegemony there. However, other experts believed that the Syrian leaders strongly desired a resolution to the Lebanese Civil War, so Syria would be free to concentrate on the conflict with Israel.

Data as of April 1987