NBC News | Ken Dilanian and Courtney Kube: The Americans were waiting for him.

Armed with a tip from informants at the airport in the Syrian capital of Damascus, the CIA knew exactly when a jet carrying Iranian Gen. Qassem Soleimani took off en route to Baghdad. Intelligence from Israel helped confirm the details.

Once the Cham Wings Airlines Airbus A320 landed, American spies at Iraq�s main airport, which houses U.S. military personnel, confirmed its exact whereabouts.

Three American drones moved into position overhead, with no fear of challenge in an Iraqi airspace completely dominated by the U.S. military. Each was armed with four Hellfire missiles.

This account of how the United States took out Soleimani is based on interviews with two people directly familiar with the details of the operation, as well as other American officials who were briefed on it.

On large screens, various U.S. officials watched as an Iraqi militia leader walked up a set of stairs to greet the leader of Iran�s Quds Force as he emerged from the airplane.

It was past 1 in the morning, so the black and white infrared imagery wasn�t very clear. No faces could be seen.

The men on the ground had no idea that their lives were now to be measured in minutes.

CIA Director Gina Haspel was observing from agency headquarters in Langley, Virginia. Secretary of Defense Mark Esper was watching from another location. Another feed was on view in the White House, but President Donald Trump was in Florida at the time.

The imagery showed two senior figures get into a sedan, which pulled away. The rest of the entourage climbed into a minivan, which sped to catch up.

The drones followed as the vehicles began moving to exit the airport. Signals intelligence specialists sought to hone in on the cellphones of the occupants to confirm their identities. Years of mapping and terrain information from satellites was available on the screens of the drone operators.

Other vehicles passed occasionally, but traffic was light. The minivan pulled ahead of the sedan.

At U.S. Central Command forward headquarters in Qatar, from where the operation was being run, there were no significant doubts about who was inside those vehicles.

Those watching could see the missiles strike, a manmade bolt from the sky. The vehicles were engulfed in a fireball. In total, four missiles were fired. There were no survivors.

Soleimani, who had helped kill Americans for more than a decade, was no more.

U.S. military officials watched a live feed of the strikes at various locations around the world. Despite the successful operation, the reaction was somber as the gravity of the attack set in and the officials contemplated what response it could unleash.

It was an operation utterly unremarkable for any technical or intelligence wizardry. It�s remarkable, rather, for how routine such lethal actions have become.

The targeted killing is the latest demonstration of how, two decades after the CIA spotted but was unable to kill a man they believed was al Qaeda leader Osama bin Laden in Afghanistan, the U.S. has become adept at hunting and killing its enemies, particularly in the troubled regions of the Middle East, South Asia and Africa.

�In less than a generation, we went from something that was abnormal and maybe even science fiction, to the point where it�s the new normal,� Peter Singer, an expert on future warfare at the New America Foundation, said. �Both leaders and the public don�t even blink an eye.�

Targeted strikes like the one that killed Soleimani represent a fundamental change in warfare, said Anthony Cordesman, who studies military trends at the Center for Strategic and International Studies in Washington.

�It requires a truly immense intelligence, surveillance and reconnaissance effort � one which basically no other country in the world can match, and which is vastly expensive, time-consuming and requires lot of expertise.�

The only thing different about Soleimani was that he was a state actor, a senior official of another government. For that reason, and in light of the expected retaliation from Iran, this strike has proven far more controversial than others. But as a technical matter, experts say, it was fairly straightforward.

Soleimani, long a shadowy presence in the Middle East, had ventured into public view in recent years, posing for pictures in Iraq and elsewhere as he plotted strategy to counter U.S. interests. So he wasn�t nearly as hard to find as bin Laden, who was hiding in Pakistan when he was killed in 2011, or the Islamic State militant group's leader Abu Bakr al-Baghdadi, who was killed in Syria during a U.S. raid in October after a yearslong manhunt.

Still, it�s not as if the Iranian put his name on passenger manifests. Tracking his travels took some doing, and knowing exactly where he would be was an intelligence feat, officials say. So was killing him in a way that risked no civilian casualties.

�These things are tricky,� one former special operator familiar with what happened said. �There is a lot that can go wrong.�

At the Baghdad airport, Soleimani was greeted by Abu Mahdi al-Muhandis, the deputy head of an Iraqi anti-American militia and a suspect in the bombing of the American and French embassies in Kuwait in 1983. Al-Muhandis got into the sedan with Soleimani and he, too, was killed in the strike.

The drones that followed the convoy are not silent, but in an urban environment like Baghdad, the sound they make is not easily discernible, officials say. There was no hint that the men in the vehicles knew they were being targeted.

The Iraqi government was not pleased by the news that the U.S. killed an official of a neighboring state on its territory without consultation. Two Iraqi security officials told Reuters that they are investigating the role of suspected U.S. informants at the Baghdad airport.

Syrian intelligence is investigating two employees of Cham Wings Airlines, Reuters reported.

U.S. officials told NBC News that they had been closely tracking Soleimani�s movements across the region for days. The Trump administration says he was planning attacks against Americans, though they have not released any evidence.

�We had specific information on an imminent threat,� Secretary of State Mike Pompeo said at a Friday news conference at the White House. �And those threats included attacks on U.S. embassies. Period, full stop.�

Iranian officials have said that Wednesday�s missile strikes against U.S. troops in Iraq, which caused no casualties, will be the end of their retaliation for the killing of their general. But U.S. intelligence officials don�t believe that.

�If I were a U.S. ambassador, I wouldn�t be starting my own car for the foreseeable future," one officials said.