BEIRUT, Lebanon — The last time the world heard from Imad Mughniyeh, he was masterminding terror spectaculars in the 1980s and 1990s — bomb attacks on American and Israeli targets, kidnappings, and hijackings.

But for nearly 15 years, no one has known exactly what the Hezbollah commander was doing. The only confirmation of his whereabouts came when he was killed February 12 in a car bombing in Syria.

Now Hezbollah officials and associates are describing a previously unknown role for Mughniyeh: Far from being too busy fleeing enemies, he was a key commander for Hezbollah in its 2006 war with Israel.

He was among the leading military and security strategists — if not the very top himself — of the group and a member of its decision-making committee, according to those who had knowledge of Mughniyeh before he was killed February 12 in Damascus.

“Hezbollah’s top architect of that war was Imad Mughniyeh,” Anis Naccache, a 57-year-old longtime associate, told the Associated Press. “You can say he was like a staff general [chief of staff].”

In a speech Friday, Hezbollah leader, Hassan Nasrallah, credited Mughniyeh with leading the group to two victories — the 2006 war and a Hezbollah guerrilla war in 2000 that led to the withdrawal of Israeli troops from its last positions in southern Lebanon.

In the 1980s, Mughniyeh was notorious in the West. He was accused of plotting suicide bombings of the American embassy and bases of American and French troops that killed hundreds, as well as the kidnappings of dozens of Westerners in Beirut.

The last attacks he is believed to have directed were suicide bombings in the 1990s against the Israeli Embassy and a Jewish center in Argentina that killed more than 100 people and a bombing in Khobar, Saudi Arabia, that killed 19 Americans.

For years, Hezbollah said almost nothing about him. But after his death, the group has embraced him as a hero — to a degree that surprised some Lebanese who believed Hezbollah would not want to revive memories of its past association with terrorism.

The 2006 war came after Hezbollah fighters captured two Israeli soldiers in a cross-border raid. Israel retaliated with a massive bombardment, then ground incursions, in a 34-day war that devastated south Lebanon.

More than 1,000 Lebanese were killed, along with 119 Israeli soldiers and 43 Israeli civilians who died from Hezbollah rocket attacks across the border.

The war ended without Israel winning any of its main objectives — regaining the two soldiers and crushing Hezbollah — and its army chief and other top commanders were forced to resign.

The fighting also held numerous surprises for the Israeli military — particularly the guerrillas’ sophisticated rockets and anti-tank weapons and their extensive preparations for battle.

Command and weapons-arsenal bunkers were dug deep into rocky hills around south Lebanon with a network of tunnels linking large storage rooms. Some exits were equipped with cameras and linked to a monitor below to help fighters ambush enemy soldiers.

Mughniyeh was apparently behind those tactics.

Mr. Naccache said the general strategy of fighting “a war of shadows” was Mughniyeh’s decision. “We were fighting Israel but Israel cannot see any fighter,” he said, speaking in English.

A Hezbollah guerrilla who was on the front lines in southern Lebanon during the 2006 fighting told AP that Mughniyeh was his commander. The guerrilla, who would identify himself only by his first name, Hassan, for fear of reprisals, would not elaborate.

Mr. Naccache, a Lebanese who once was a fighter for Palestinian leader Yasser Arafat’s Fatah faction and has known Mughniyeh since Mughniyeh was 13, said the two met dozens of times over recent years.

The last time was in Lebanon two months before the 2006 war. During that meeting, Mr. Naccache said, Mughniyeh showed him photographs of anti-tank rockets that Hezbollah had recently obtained, the Russian-made Kornet and the RPG-29.

He said Mughniyeh explained to him how the rockets could be used against Merkavas, the massively armored tanks that are vaunted as symbols of Israeli military might. Mr. Naccache said Mughniyeh “had studied the exact millimeters of the thickness of a Merkava and what was the best point from which to hit the Merkava.”

“I understood how serious he was in his preparation for the war,” Mr. Naccache said. Mughniyeh did not tell him where Hezbollah obtained the weapons, he said. Iran is believed to be Hezbollah’s main arms supplier, with some coming from Syria.

Mr. Naccache, as a Sunni Muslim, is not a member of the Shiite group Hezbollah but is a close supporter of the organization and a longtime associate of Mughniyeh. He taught Mughniyeh when he showed up at age 13 at a Fatah camp south of Beirut and asked to be given guerrilla training.

Naccache served 10 years in prison after trying assassinate Iran’s last prime minister under the monarchy, Shapour Bakhtiar, on Iran’s behalf in Paris in 1980. A policeman and bystander were killed.

Israeli defense officials, speaking on condition of anonymity because they were not authorized to speak to the press, said Mughniyeh was in charge of Hezbollah’s overall military effort, serving as something like a defense minister, and influenced war strategy.

Officially, Israel has denied involvement in Mughniyeh’s killing. Privately, Israeli defense officials will neither confirm nor deny foreign reports attributing the assassination to Israel.

Israeli officials have made little secret of their satisfaction he is dead. Israeli officials also said Mughniyeh had long been wanted and denied reports that there was ever any tacit agreement with Hezbollah not to go after him.

But the officials, speaking on condition of anonymity because of the sensitivity of the matter, acknowledged Mughniyeh’s profile was raised by the 2006 war. Israel also believed Mughniyeh was planning a large attack to avenge Israel’s airstrike in Syria in September. Israel has said little about that airstrike, which foreign reports have said might have targeted a nuclear installation in Syria. Hezbollah and Iran have accused Israel in the car-bomb death, and Mr. Nasrallah has vowed retaliation.

The question now is how seriously Mughniyeh’s loss will affect Hezbollah. The organization is known for absorbing blows such as the loss of major figures.

Mr. Naccache said Hezbollah is “very structured and [has] many people with experience. They have the same experience as Hajj Imad not less.”