The US missile strikes offer no guarantee if they will cause serious damage to Bashar al Assad’s chemical weapons infrastructure.
Paul Walker, a chemical weapons expert, explains why the Syrian regime led by Bashar al Assad continues to rely on chemical warfare.
Walker has closely worked with several governments around the world for three decades on non-proliferation of chemical weapons.
He is also the director of the Green Cross International’s Environment Security and Sustainability programme. In past, he has advised the Armed Services Committee in the US House of Representatives.
Do you think the US missile strikes will be effective in dismantling Bashar al Assad’s chemical weapons?
PW: No, there is no guarantee that we can identify all sites related to chemical weapons production, storage, and use, especially small operations.
On the other hand, we certainly are aware of the former major research, development, production, and storage sites in Syria.
We also can identify the airbases where aircraft and helicopters are located related to these attacks.
So any US and NATO (North Atlantic Treaty Organisation) military strikes will likely attack these chemical weapons-related sites, possibly even including the major research lab.
The US, UK and France have known for years that Assad's regime possessed chemical weapons. Why didn't they act against it earlier?
PW: Many countries, which are parities to the Chemical Weapons Convention (CWC), knew long ago that Syria possessed chemical weapons.
The former head of the Russian chemical weapons programme was in fact arrested after visiting Damascus several times in the mid-1990s, likely helping Syria build chemical stockpile - this was prior to the CWC entering into force in 1997.
Former US President Barack Obama did indeed warn of a "red line" in Syria after the August, 2013, sarin nerve agent attack in Ghouta.
But the US and other allies did not attack Syria militarily then due to Syria's accession to the CWC and Assad's agreement to declare and destroy his full CW stockpile.
It was only much later when the OPCW's Fact-Finding Mission (FFM) found forensic evidence of the use of chemical weapons that everyone realised that Syria was still using chemical weapons against rebel forces and violating the CWC.
Nevertheless, both Syria and Russia have completely denied that Syria possessed or used any chemical weapons.
US President Donald Trump's attack on Syria in April, 2017, shortly after the Khan Shaykoun attack, was the first military response.
So the Syrian regime's stockpile of chemical weapons was supposed to be dismantled after it acceded to the Chemical Weapons Convention in 2013. Why didn't that arrangement work?
PW: Syria declared 1,308 metric tons of chemical agents and precursor chemicals to the OPCW in October, 2013.
All of these dangerous chemicals were moved to Latakia and then removed from Syria to be destroyed on board the USS Cape Ray and also in four countries, Finland, Germany, the UK, and US.
These chemicals were fully neutralised or burned by December, 2015. It's now apparent that the Syrian authorities either did not declare all of its chemical agents, or produced more sarin agent since its initial declaration to the OPCW.
Chlorine, which Syria has used numerous times, is a dual-use industrial chemical and is not part of a country's declaration.
The Declaration Assessment Team (DAT) of the OPCW has visited Damascus at least 15 times since 2013 to try to answer remaining discrepancies in Syria's declaration, but has been unsuccessful to date.
So Syria has clearly violated its obligations under the Chemical Weapons Convention (CWC) by hiding chemical agents or precursor chemicals.
The Syrian regime and its key ally, Russia, blame rebels for staging chemical attacks. Can this be true?
PW: I have not seen any convincing evidence that rebel forces are capable to using chemical weapons, and most CWC States Parties do not believe the Syrian and Russian explanations.
All of the forensic evidence and eye-witness reports in Syria have found that the chemical agents have been dropped from helicopters and aircraft, including improvised barrel bombs.
And the rebel forces do not have any helicopters or aircraft.
The Syrian and Russian statements before the OPCW in The Hague, and also before the UN Security Council, are widely viewed as lies.
So there were strong grounds for the US and others to act?
PW: Most, everyone is very frustrated with the continued use of chemicals as weapons in Syria. It's also surprising that Russia, a close ally of Syria, seems unable to convince Syria to stop using chemical weapons.
This has led to the establishment of the "International Partnership against Impunity" and very strong statements against any use of any chemicals as weapons at the OPCW in The Hague.
The use of sarin nerve agent last year in Khan Shaykoun, plus the most recent reported chlorine attack in Douma, combined with Russia's veto of the JIM's renewal, has pushed the US and other countries to the look more towards military options.
How many times has Assad used chemical weapons?
PW: The large majority of deaths and casualties in the long Syrian war have been a result of conventional bombings and attacks by the Syrian and Russian militaries, not from chemical weapons attacks.
Chemical weapons, including mustard and sarin agent and chlorine, have been used well over 100 times, but have killed fewer than 2,000 people, a small percentage of the hundreds of thousands killed since 2012.
All 192 States Parties to the CWC have agreed that chemical weapons, although deadly, are no longer an effective military weapon - this is the primary reason that both the US and Soviet Union agreed bilaterally in the mid-1980s to unilaterally and reciprocally destroy their enormous chemical arsenals.
However, toxic chemicals can still be used effectively as a terror weapon, especially against defenceless civilian populations, and that is apparently what both the Syrian military and Daesh have decided.
Chemical agents are also heavier than air, so if families are hiding in basements, chlorine and other toxic chemicals can easily impact them.
The interview has been edited for clarity.