Imad Mughniyah, Hezbollah's international operations chief, was eliminated in a clandestine joint operation by American CIA and Israel's Mossad in 2008, in a move sanctioned by then US President George Bush.
The script of the whole operation, including the planning and the execution, has now been laid bare by former security officials, The Washington Post has reported.
The Bush administration had long regarded Hezbollah, and particularly Mughniyah, as a threat to the United States, given his involvement in the US embassy bombing in Beirut that killed 63 people, including eight CIA officers, and his suspected role in training Shiite militias against US forces in Iraq.
Mughniyah was also involved in the kidnapping, torture and killing of CIA's station chief in Lebanon, William F. Buckley, in 1984.
The senior Hezbollah figure featured prominently on FBI's Most Wanted Terrorists list with a $5 million reward on his head.
Israel joined in Mugniyah's assassination to seek 'revenge' for his role in the 1992 suicide bombing of the Israeli Embassy in Buenos Aires that killed four Israeli civilians and the 1994 attack on a Jewish community center in the city that killed 85 people.
How CIA, Mossad Took Down Mughniyah
The first step in the operation to kill Mugniyah was taken in 2002 in a secret meeting in Israel between senior officers of U.S. military's elite Joint Special Operations Command and the chief of the Israeli military intelligence service.
A former U.S. official revealed how the Israeli officials were shocked when the JSOC first suggested a plan to kill Mugniyah in a matter-of-fact manner.
"When we said we would be willing to explore opportunities to target him, they practically fell out of their chairs," the official said.
However, another former intelligence official said that it was the Israelis who first approached the CIA for a joint operation to kill Mughniyah after he was traced to Damascus in 2007, a year before he was killed.
The CIA and Mossad reportedly monitored Mughniyah in Damascus for months before charting out a plan to assassinate him, the former officials told the Post.
Both intelligence agencies then worked on studying Mughniyah's "pattern of life" observing his routine to identify the right time and place to assassinate him.
CIA officers had reportedly stayed in a safe house in a building near Mughniyah's apartment.
The officials also revealed to the Post that it was the United States that built the bomb that ultimately killed the Hezbollah terrorist.
Bombs were tested at least 25 times to ensure it would not cause collateral damage,
The tests were carried out at Harvey Point, a facility in North Carolina, the very venue where the CIA later built a replica of Osama bin Laden's compound in Abbottabad, Pakistan.
On the night of 12 February, 2008, the agencies used facial recognition technology to confirm Mughniyah's identity after he walked out of a restaurant in his neighborhood, watched closely by CIA agents.
As he approached a parked SUV, agents in Tel Aviv pulled a trigger to set off a bomb planted in a spare tire on the back of the vehicle.
Mughniyah was killed instantly in the explosion.
Assassination Pushed Legal Boundaries
Experts beleive that CIA's killing of Mughniyah violated the 'oldest battlefield rules' , as the US killed him in a country where it was not at war, and with tactics matching those of terrorists.
"It is a killing method used by terrorists and gangsters. It violates one of the oldest battlefield rules," Mary Ellen O'Connell, a professor of international law at the University of Notre Dame told the Post.
However, the officials suggested that the use of the car bomb was hardly debated in the Bush administration, and that they justified the assassination with the theory of national self-defence.
How US, Israeli officials reacted to Mughniyah's death
"When I heard about it, I was one damn happy man," Ryan C. Crocker, the U.S. ambassador in Iraq said when Mughniyah was killed.
"All I can say is that as long as he drew breath, he was a threat, whether in Lebanon, Iraq or anywhere else. He was a very intelligent, dedicated, effective operator on the black side," he said.
In 2008, several months after he was killed, Michael Chertoff, then secretary of homeland security, said: "To be honest, they (Hezbollah) make al-Qaeda look like a minor league team".
After Hezbollah blamed Israel for Mughniyah's death, the office of then Israeli Prime Minister Ehud Olmer said: "Israel rejects the attempt by terror groups to attribute to it any involvement in this incident. We have nothing further to add."