JERUSALEM — Hezbollah’s evolution from its creation after Israel’s 1982 invasion of Lebanon to its current role in provoking a major military confrontation underscores how far the group has come and how it continues to be a force with which Israel must contend.

Under the leadership of Sheik Hassan Nasrallah, Hezbollah is one of the strongest and best organized bodies in Lebanon. Nasrallah is both a determined man of religion and a master of psychological warfare. He’s manipulative and knows how to drag people behind him.

With 20,000 troops and at least 10,000 rockets trained on northern Israel, Hezbollah remains a potent force in Lebanon — the only remaining private militia in fact, after others were disarmed.

Its popular strength also derives from its civilian arm: It runs hospitals, schools, food-distribution centers, orphanages and a television station, partly thanks to an estimated $60 million in annual aid from Iran.

When Israel invaded Lebanon in 1982 to rout out Palestinian terrorist activity across its northern border, relations between Israel and Amal, a Shi’ite political and paramilitary organization, were cordial.

Amal represented the weakest strata of Lebanese society, and its interests were served by Israel’s weakening of Palestinian power in Lebanon.

But soon the young Nasrallah followed his teacher, Abbas Musawi, out of Amal, and the radical group Hezbollah — the party of God — was formed.

Iran sent a force of some 1,500 Revolutionary Guards to help the new organization, whose main focus was to expel Israeli and Western forces from Lebanon.

As anti-Israeli operations in Lebanon intensified, an Israeli missile struck Musawi’s motorcade in 1992 and killed him. It was Iran’s spiritual leader, Ayatollah Khamenei, who asked Nasrallah to replace Musawi. Today Iran and Syria are Hezbollah’s main patrons, supplying the organization with arms and funds.

Hezbollah views the Iranian model of an Islamic state as the most desirable form of governance. Given Lebanon’s religious diversity, however, Hezbollah does not consider an Islamic state there a viable political option.

Running in June 2005 elections, Hezbollah won 23 seats in Lebanon’s 128-member Parliament, and holds the Energy Ministry. Some hoped that political power would moderate the group and compel it to act more responsibly, but there has been little indication of a change in Hezbollah’s outlook or behavior.

Hezbollah supports the destruction of Israel and cooperates with other militant Islamic organizations, such as Hamas, to promote this goal. Analysts see increased coordination lately among Hamas and Hezbollah.

Hezbollah attacks on the Israel Defense Force were an important factor in Israel’s decision to evacuate its southern Lebanon security zone in May 2000.

At first, Hezbollah also targeted other Western forces in Lebanon, particularly the French and Italian multinational peacekeeping force, whose purpose was to stabilize the country.

Hezbollah was believed to be the driving force behind several attacks on Western targets: the April 1983 suicide bombing at the U.S. Embassy in Beirut that killed 63 people; the October 1983 attack on the U.S. Marine barracks in Beirut that killed 241 troops; and a simultaneous attack on the French multinational force headquarters that killed 58 French soldiers.

In September 1984, seven months after U.S. forces withdrew from Lebanon, Hezbollah supporters staged a second attack on the U.S. Embassy annex in Beirut. Twenty more people were killed.

In addition, elements of Hezbollah have been linked to involvement in the kidnapping, detention and torture of some 30 American and other Western hostages between 1982 and 1992. Among the hostages were U.S. Army Col. William Higgins and William Buckley, the CIA’s Beirut station chief.

During the Israeli occupation of southern Lebanon, Hezbollah fought the IDF and the Israel-backed South Lebanese Army. It refused to disarm itself, in violation of the 1990 accords that ended Lebanon’s civil war.

Hezbollah also has ignored U.N. Security Council resolutions ordering that it disarm, feeling it has political backing from Iran and Syria and popular support because of its successful guerrilla warfare against Israel.

“For us Lebanese, Hezbollah is a national resistance movement,” Lebanese President Emile Lahoud once said. “If it wasn’t for them, we couldn’t have liberated our land.”

Hezbollah has continued fighting Israel even after the Israeli withdrawal, inventing a claim to the Shebaa Farms area of the Golan Heights and demanding that Israel evacuate that area too. Israel has refused, claiming that the farms were territory captured from Syria in the 1967 Six-Day War, not Lebanese territory.

The United Nations backed the Israeli position and rejected Hezbollah’s claim, but the group has used the dispute as a pretext to launch Katyusha rockets into Israel and occasionally open fire on soldiers along the border.

Shortly after the withdrawal, Hezbollah killed three Israeli soldiers in a cross-border attack and brought their bodies back to Lebanon. The group later kidnapped Israeli businessman Elhanan Tannenbaum, a colonel in the Israeli army reserves, which led to an exchange of prisoners on Jan. 29, 2004.

Israel exchanged some 30 Lebanese and Arab prisoners, the remains of 60 Lebanese militants and civilians, 420 Palestinian prisoners and maps showing Israeli mines in southern Lebanon for Tannenbaum and the remains of the three IDF soldiers.

Among the released Lebanese prisoners were Shi’ite activist Mustafa Dirani and Sheik Abdul Karim Obeid, one of the leaders of Hezbollah.

Hezbollah promises to provide new information on the fate of IDF navigator Ron Arad, who was taken hostage after bailing out of his plane on a 1986 mission over Lebanon, have proved empty.

Palestinian terrorist groups have been known to draw inspiration from Hezbollah’s success fighting Israel, and Israel says Hezbollah increasingly is involved in training and arming Hamas. Israel also has blamed Hezbollah for attempts to draw Israeli Arabs into terrorist activities.

When Jordan arrested Hezbollah members trying to smuggle Katyusha rockets into the West Bank, Nasrallah said, “It is a duty to send arms to Palestinians from any possible place.”