The assassination of a top operative for the Lebanon-based group Hezbollah was both a surprise and a puzzle for many people. Imad Mugniyeh was a wanted man for some of the most spectacular terrorist attacks of the 1980s and 1990s, but remained little known outside intelligence and counterterrorism circles. As VOA correspondent Gary Thomas reports, his low profile is what kept him alive this long.

Imad Mugniyeh was a superstar of the terrorism world in the 1980s.

Based in Beirut, he is believed by counterterrorism experts to be the chief planner of numerous attacks over the past quarter of a century, including the 1983 bombings of the U.S. embassy and the U.S. Marine barracks in Beirut. He is credited with pioneering the widespread use of suicide bombers, which has since become the favored tactic of Islamic extremists.

But he was gradually eclipsed by a new generation of violent Islamic radicals led by a young Saudi named Osama bin Laden.

Andrew Cochran, editor of the Counterterrorism Blog website, says bin Laden drew both inspiration and terrorist tactical knowledge from Mugniyeh.

"Bin Laden definitely took inspiration, and told him so," he said. "And there definitely were ties between Mugniyeh and bin Laden and al-Qaida stretching back years. It's just that Mugniyeh did not do the kind of media that bin Laden, al-Zawahiri, and the rest of al-Qaida do online."

Counterterrorism analysts say Mugniyeh spent much of the time trying to stay out of sight. Although based in Lebanon, analysts say he took refuge in Iran for long periods, attempting to stay under the radar of the world's terrorist hunters, and he seemed to have become dormant. There were even reports that he had retired from active duty as Hezbollah evolved from a small terrorist organization into more of a political and military force.

But Douglas Farah, an author and counterterrorism consultant, does not think that Mugniyeh had retired.

"He was fairly young when he died," he said. "He was not an old man who needed to get out of the field. His operational thinking was still highly valued. And I would think that it would have been highly unlikely that he had simply gone into retirement."

Reva Bhalla, an analyst with the private intelligence firm Stratfor, says that just before his death, reports began surfacing that Mugniyeh was back in the terrorist game.

"We started getting these reports from some of our sources that he had become active again," Bhalla said. "And that really made us sit upright, and we're like 'wow' because Mugniyeh, this is the guy who is a real creative thinker. He really knows how to get all the tactical details down to pull off a really successful attack outside of the region especially."

As police often say, a murderer must have both motive and opportunity. Given Mugniyeh's past history, there is no shortage of suspects with a motive - the United States, France, Britain, and Israel.

But analysts say there are far fewer suspects with opportunity. He was killed in Syria, which is one of Hezbollah's sponsors and where security is supposed to be tight.

Hezbollah and its other sponsor, Iran, have blamed Israel. Israel has denied responsibility for Mugniyeh's death.

But Stratfor's Reva Bhalla says Israel is the most logical suspect because the bombing has the hallmarks of precision planning and extraordinary intelligence work.

"He was obsessed with operational security. He was very, very good at moving around," Bhalla said. "But once you start becoming operational again, once we started hearing these reports, the risk went up that he would be vulnerable to some kind of leak. And it looks like that's what was the case in this. This was a very brilliant attack the way it was pulled off. You had to have incredibly good intel [intelligence] to be waiting there, have the bomb set up, and pull it off that well."

Some analysts say the assassins also had a high sense of irony or a macabre sense of humor. Imad Mugniyeh was killed by a car bomb, a tactic that he himself had used so often in the past to deadly effect.