The Pentagon says the Syrian chemical weapons program has been set back years after producing visual slides to prove the effectiveness of the West's missile attack.
More details began to emerge from the Pentagon about the three targets the American military struck in Syria in conjunction with British and French forces.
The coalition hit the Barzah Research and Development Centre outside Damascus with 76 missiles, destroying the facility and setting back Syrian chemical weapons capabilities "for years," the US military said in an initial assessment.
The second and third targets were part of what the US military described as the Him Shinshar chemical weapons complex outside the city of Homs. The military said the strikes "completely destroyed" the complex's chemical weapons storage facility and "successfully hit and sustained damage" to the installation's chemical weapons bunker.
"We deployed 105 weapons against three targets that will impact the Syrian regime's ability to develop, deploy and use chemical weapons in the future," Marine Corps Lieutenant General Kenneth McKenzie, director of the Joint Staff, said during a news conference. He described the facilities as "fundamental components of the regime's chemical warfare infrastructure."
McKenzie conceded that "the Syrian regime knows that we've been looking at these targets for a long time" and that it is possible the Syrian military had evacuated people or stockpiles in advance. But "there's material and equipment associated with each of these sites that was not movable," he said, adding, "That's what really sets them back."
To conduct the strikes, the US military joined forces with British and French units and launched from air and naval platforms in the Red Sea, Gulf and the Eastern Mediterranean.
In early 2017, inspectors from the Organisation for the Prohibition of Chemical Weapons visited the Barzah facility. The site is part of the Syrian Scientific Studies and Research Center (SSRC), an organisation the US Treasury calls "the Syrian government agency responsible for developing and producing non-conventional weapons and the means to deliver them."
The United States imposed sanctions on 271 personnel from the SSRC last year in response to a sarin attack on civilians in Khan Sheikhoun. The Treasury said the staff had expertise in chemistry and related disciplines and had worked in support of the SSRC's chemical weapons program since at least 2012.
The Trump Administration conducted a missile strike against one of Assad's air bases last year in April in response to the chemical weapons usage in Khan Sheikhoun.
A report by the BBC shortly after last year's strike found that the Syrian Government continued to manufacture chemical weapons at research facilities.
Citing a Western intelligence document, the BBC reported that the Syrian Government was making chemical weapons at three SSRC sites, including the one in Barzah that the coalition of US, British and French forces said it destroyed.
The Western intelligence report, according to the BBC, found that the Barzah facility specialised in installing chemical weapons on long-range missiles and artillery.
Less is known about the facility that was attacked outside Homs.
In the 1980s, the New York Times reported a story about an air base outside Homs, known as Shinshar, where the Soviet Union was installing antiaircraft missiles, aimed primarily at fending off Israeli attacks.
Rumours of an underground chemical weapons storage facility in Shinshar emerged in the aftermath of the US invasion of Iraq amid the search for Saddam Hussein's weapons of mass destruction.
The British Defense Ministry said the strike outside Homs targeted a former military base about 25km west of the city "where the regime is assessed to keep chemical weapon precursors stockpiled in breach of Syria's obligations under the Chemical Weapons Convention."
Britain said that "very careful scientific analysis" was used to determine where best to target British missiles to maximize the destruction of the stockpiled chemicals and minimise the risk of contaminating the surrounding area.
"The facility which was struck is located some distance from any known concentrations of civilian habitation, reducing yet further any such risk," the British Defence Ministry said.
The Pentagon said the chemical weapons storage facility and a chemical weapons bunker were targeted at the site outside Homs.
McKenzie said initial assessments indicated that the storage facility was destroyed but that the bunker facility was "successfully hit and sustained damage," suggesting the Pentagon wasn't confident the strikes had fully obliterated the underground complex or hadn't intended to do so.
It wasn't clear if the facilities the New York Times and Syrian journalists referenced in Shinshar were the same as the complexes the military struck. The Pentagon described the facility as being west of Homs, whereas the village of Shinshar is due south.