The Syrian civil war has turned into a fully-blown regional conflagration. Shia Muslim groups are on one side, linked across Lebanon, through Syria, to Iraq and Iran. On the other side are Sunni Arabs, including Islamic State extremists, backed by the Arab Gulf states for whom the Islamic Republic of Iran is a primary foe. The deep involvement of the powerful Shia group Hezbollah, based in Lebanon and supporting Syria’s al-Assad regime, is a major factor in the ongoing conflict. Fighting has now spilled over to Hezbollah’s home territory.