AREA -- Lebanon's total area is 4,105 square miles, slightly smaller than Connecticut. The province of southern Lebanon makes up about one-fifth the country's total area. Beginning at the Israeli border, the first sector is a 140-square-mile enclave controlled by a Lebanese Christian militia supported by Israel, a strip of hilly terrain ranging from a half mile to six miles in depth and stretching about 60 miles from the Mediterranean to the foothills of Mt. Hermon. To the north is a 430-square-mile sector controlled by U.N peacekeeping forces. To the north of that is a less clearly defined area controlled by Palestinian and leftist Lebanese Moslem guerrillas that blends into the rest of Lebanon, which is under central government and Syrian peacekeeping forces' control.

POPULATION -- Lebanon's population is about 3 million, plus about 400,000 Palestinians. About one-sixth of the total population lives in southern Lebanon. A much larger portion lived there before hostilities began. The population of the Christian-controlled enclave fluctuates by season, from an estimated 80,000 to 100,000. About 65 percent are Shiite Moslem, about 30 percent Christian and 5 percent Sunni Moslem and Druze. In the U.N. area, the civilian population is about 200,000, almost all Shiites. Because the third tier of southern Lebanon -- that controlled by PLO and Moslem guerrilas -- is not precisely defined, population estimates are not available, but it is at least as high as that of the U.N. zone.

HISTORY -- Lebanon, an ancient maritime culture, came under Ottoman control in modern times and, after World War I, was made a French mandate by the League of Nations. It became independent in 1943, and its history for the next three decades was one of tenuous accommodation between the nearly equal Christian and Moslem populations, with occasional outbreaks of hostility. A civil war fought in 1975-76 brought the country to the verge of disintegration and a Syrian-dominated Arab peacekeeping force entered the country, which has splintered into spheres controlled by various factions and their militias. In 1978 Israel, declaring a need to wipe out sites from which Palestinian guerillas launched several terrorist attacks against Israeli civilian settlements, invaded southern Lebanon. It later withdrew its forces, but continues to patrol and control the southernmost portion of Lebanon.

FORCES -- Southern Lebanon has become one of the more curious war zones in modern history, with its layered sub-sectors forming a gigantic free-fire zone:

Starting at the Israeli border, the first layer is the Israeli-armed Christian Lebanese forces of Maj. Saad Haddad, which face their only militarily active front to the north. They include some 500 former Lebanese Army regular troops and as many as 1,500 Shiite Moslem irregulars.

From "Haddadland" north to the Litani River -- with the exception of a pocket around the port of Tyre and a gap north of Haddad's battered capital of Marjoyoun -- stand the roughly 6,000 men from 11 countries making up the U.N. peacekeeping force. From the south they are harassed by Haddad and from the north and west increasingly by the Palestine Liberation Organization and its leftist and radical Lebanese allies known as the National Movement. Occasionally Amal, a political and paramilitary organization of the overwhelmingly Shiite Moslem population in the south, tries to protect residents from all the other belligerents but they share with the U.N. forces the disadvantages of being underarmed.

North of the Litani River, the Palestinians and their leftist allies exercise a kind of wild and woolly control, but they are hemmed in by the Syrian Army, which came to Lebanon as a peacekeeping force in 1976