BEIRUT — Syria has a long and tumultuous history of meddling into Lebanese affairs. For much of the past 30 years, the seven-times-smaller Lebanon has lived under Syrian military and political domination. Damascus has often stirred tensions within Lebanon's explosive sectarian mix of Christians and Muslims to advance its regional interests, including during the country's 15-year civil war that ended in 1990. Syria's powerful allies in Lebanon include the Iran-backed militant group Hezbollah. Important milestones affecting the Syria-Lebanon relationship:

SYRIA'S CIVIL WAR: Since the uprising against President Bashar Assad began in February 2011, Lebanon has been steadily drawn into the unrest — a troubling sign for the country with political parties rooted in various Christian and Muslim sects, many of which are armed. While Syria's revolt has intensified between predominantly Sunni rebels and Assad's regime — dominated by Alawites, an offshoot Shiite group — Lebanon has seen a steady flow of refugees from Syria, with frequent street clashes along its northern border. Lebanese Prime Minister Najib Mikati, who heads a government dominated by Hezbollah and other pro-Syrian groups, has led a policy of "disassociation" from its influential neighbor. Damascus has accused Sunni groups in Lebanon of supporting rebels by trying to establish a supply line to anti-regime fighters across Lebanon's northern border.

Tensions between Beirut and Damascus deepened in August, after an arrest of former Lebanese Information Minister Michel Samaha, one of Syria's most loyal allies in Lebanon. A senior Lebanese police official, speaking anonymously because he was not authorized to talk to the media, said Samaha confessed to having personally transported explosives in his car from Syria to Lebanon to kill Lebanese. A military court indicted Samaha; Syrian Brig. Gen. Ali Mamlouk, a close aide of Assad, was indicted in absentia on charges of furnishing the explosives.

POLITICAL ASSASSINATIONS: Political assassinations in Lebanon have occurred with impunity for decades, and Syria has been blamed for many of the killings. In 2005, Syria was widely accused of involvement in the killing of former Prime Minister Rafik Hariri, a wealthy businessman and an influential Sunni politician. Hariri was hailed in Lebanon for rebuilding Beirut after the 15-year civil war. Following his death in a car bomb explosion, Damascus was forced to withdraw its troops and Syria's grip in Lebanon began to slip. The U.N.-backed Special Tribunal for Lebanon has indicted four Hezbollah members as suspects in the Hariri assassination. Hezbollah denies involvement in Hariri's killing and has refused to extradite the suspects.

Many Lebanese residents accused Assad's regime of being behind Friday's assassination of Brig. Gen. Wissam al-Hassan, a Sunni, who headed the intelligence division of Lebanon's domestic security forces that has been probing the assassination plot against Hariri. Al-Hassan and his agents have been credited with identifying Samaha, the former information minister, as Syria's link to Lebanon. Damascus has condemned the bombing.

HEZBOLLAH: The Iran-backed Hezbollah has been Syria's most powerful ally in Lebanon, particularly since Damascus ended its military presence in Lebanon seven years ago. The Shiite militant group has dominated Lebanese politics for more than a decade and is now in control of the government. In 2006, Hezbollah gained support from Sunnis and Christians during a 34-day war with Israel, although Lebanon's southern villages and towns and the predominantly Shiite suburbs of Beirut sustained heavy damage.

Opponents of Assad's regime say Syria's embattled president has maintained his influence in Lebanon through allies such as Hezbollah.

Since the beginning of the Syrian uprising, Hezbollah has sought to distance itself from the turmoil in Syria, although there have been allegations that the group has sent fighters to help Assad's regime fight rebels. Hezbollah's leader, Sheik Sheik Hassan Nasrallah, has not publicly sanctioned any operations in support of Assad, and warned the mayhem in the neighboring country was out of the group's control.

TROOPS ON THE GROUND: Lebanon's 15-year civil war ended in 1990 with Syrian forces defeating opponents, controlling large parts of the country and installing allied governments in Beirut. Syrian forces moved into Lebanon in 1976 as peacekeepers after the country got engulfed in civil war between Christian and Muslim militias.

Syrians were drawn into the conflict, and clashed with the Israeli troops after the 1982 invasion aimed at driving out Palestinian guerrillas. In 2000, Bashar Assad became president of Syria, succeeding his late father, Hafez Assad. Israel withdrew from South Lebanon, increasing pressure on Syria to leave. Syrian troops pulled out five years later, after sweeping street protests following Hariri's assassination. Many in Lebanon and its Western-backers blamed Syria for the killing. Damascus has denied involvement.