REUTERS/Bassam Khabieh A man mourns the victims of a chemical weapons attack in Ghouta, Syria.

Inspectors tasked with ridding Syria of its chemical weapons were surprised to discover that many of the production facilities were hidden in plain site, including aboard 18-wheeler trucks disguised as moving vans, the Wall Street Journal has reported.

Syrian president Bashar Assad went to great lengths to hide Syria’s chemical weapons program from the world. The regime’s use of sarin nerve gas — a highly toxic chemical warfare agent banned under international law — came under intense scrutiny after 1,500 Syrian civilians died from exposure to the gas in a 2013 regime attack outside of Damascus.

President Barack Obama backed down from his plan to launch limited airstrikes against the regime in response to the mass killing after Syria agreed, as part of a US-brokered and Russian-backed deal, to have its entire chemical weapons stock removed from the country and destroyed at sea.

Upon arriving in Syria in October 2013, however, inspectors with The Hague-based Organisation for the Prohibition of Chemical Weapons (OPCW) were surprised to discover how extensive and sophisticated the regime’s chemical weapons program really was.

From the Journal:

Among the biggest surprises for the inspectors was Syria’s fleet of mobile chemical-weapons production facilities, housed on 18-wheeler trucks. They looked so much like regular trucks that they even carried advertisements, including one for a Hungarian moving company.

The mobile factories were designed to look as innocuous as possible to avoid being targeted by airstrikes. They appeared so harmless, the Journal noted, that inspectors later compared them to Transformers toys.

REUTERS/George Ourfalian A Syrian man is treated after being exposed to sarin nerve gas.

Inside those labs, regime scientists were brewing chemicals to create sarin nerve gas, which was then fed into a warhead and attached to a missile.

It was “unlike any other program that I’ve seen or read about,” chemist and inspector Scott Cairnes told the Journal.

Experts and officials warned US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov, who negotiated the deal, that it would be nearly impossible to eradicate Assad’s entire chemical weapon arsenal — especially in the midst of a brutal civil war.

As it turns out, the critics were largely correct: on June 23, 2014, the last of Assad’s declared chemical weapons were supposedly shipped out of Syria for destruction. Earlier last month, however, traces of sarin-type chemical weapons and ricin-type biological weapons were found by inspectors at sites the Assad regime had failed to report to the Organisation for the Prohibition of Chemical Weapons.

The Obama administration reportedly knew about those undeclared sites.

“We knew of sites that Assad didn’t declare,” a senior intelligence official told Bloomberg. “It’s a balancing act. You want to do something to get rid of it, but you also don’t want to show them all your cards.”

In June, Syrian doctors testified before Congress about the regime’s continued use of chemical weapons to kill its citizens. Video was shown of children foaming at the mouth after the poisonous gas had seeped into their basement.

Inspectors claim they were suspicious of the regime’s claim that it had only 1,300 tons of chemicals that could be used to produce sarin gas, but were limited in the number of production facilities they could visit due to security concerns and government-imposed restrictions.

“We had no choice but to cooperate with them,” Cairns told the Journal. “The huge specter of security would have hampered us had we gone in there very aggressively or tried to do things unilaterally.”

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