Ninety percent of Syria’s declared chemical weapons have now been shipped out of the country, but in recent days disturbing reports have emerged of at least nine attacks using chlorine gas. Rebel forces and the government have traded blame for the attacks, the worst of which killed two and sickened more than 100 in the rebel-held village of Kafr Zita on April 11, though the method of dispersal—barrels dropped from a helicopter—certainly fits with the tactics used by Bashar al-Assad’s forces.
Chlorine is a widely available chemical with many perfectly legitimate industrial uses—water purification being the most well-known—and wasn’t included in Syria’s declaration of its chemical arsenal. It’s almost never used as a weapon today, and its appearance in Syria harkens back to the earliest days of chemical warfare.
Though chemicals including tear gas and sneezing powder were used in the early days of World War I, the first mass gas attack in history was carried out by German forces at the Battle of Ypres, in Western Belgium, on April 22, 1915—and chlorine was the weapon of choice. Fritz Haber, the German chemist who also helped develop fertilizers that probably saved millions of lives over the course of the 20th century, is somewhat unfairly best remembered for the development of this deadly and terrifying weapon.
When inhaled, chlorine inflames the lung tissues, allowing fluid to enter the lungs from the bloodstream. In the worst cases, victims drown on the fluid building up in their lungs, though it takes extremely high doses to kill. For reference, chlorine is about 3,000 times less toxic than the sarin gas that killed hundreds of people in a chemical attack in Syria in August.
At Ypres, the Germans launched a massive and concentrated attack, manually releasing the gas from hundreds of cylinders and allowing prevailing winds to blow a cloud of gas over the French and French colonial lines. Edward Spiers, a professor of strategic studies at the University of Leeds and author of A History of Chemical and Biological Weapons, described the effect in an interview with Slate today.
“Because it was the first time, there was tremendous shock, and the French forces weren’t prepared at all and started to run,” he said. “The worst thing you can do in a chemical cloud is run because then you breathe more deeply. They were inhaling more and more chlorine and the casualties were quite high and the Germans gained a considerable amount of ground.”
The number of French soldiers killed in the gas attack may have been as high as 6,000. The Germans would use chlorine several more times, and the British employed it at the Battle of Loos, but it’s effectiveness diminished as soldiers became better prepared for it. Early countermeasures were as simple as breathing through handkerchiefs soaked in urine, but eventually proper respirators were developed for the battlefield. In the escalating chemical arms race, chlorine fell out of favor compared with deadlier chemicals like phosgene and Mustard Gas.
Use of chlorine by armies has been basically unheard of since the Great War. In the international Chemical Weapons Convention, drafted in the 1990s, its use as a weapon is prohibited, but as a chemical, it is not banned outright due to its civilian uses. “The old lung agents like chlorine and phosgene were put on the back burner because nobody thought they’d be used,” says Spiers.
It has reappeared as a weapon at least once since World War I. In Iraq in 2007, insurgents experimented several times with using chlorine-packed tanker trucks in suicide bombings. This wasn’t a particularly brilliant idea. Explosives actually make chlorine less effective—they simply burn the gas up—and the casualties weren’t any greater than from normal truck bombs. The reports of poison gas were certainly unnerving to the general population, though.
Aside from its easy availability, Spiers says chlorine has one major advantage: Unlike nerve agents such as sarin, you can instantly see and smell the cloud.
“Gas warfare has always been as much a psychological weapon as a weapon that kills and injures,” he says. “Seeing the gas coming towards you can cause more panic than not knowing it’s there. Because it’s capable of terrorizing, some of the more primitive weapons used against completely unprotected civilian communities can be extremely effective.”
The Syrian regime has often favored weapons that seem tactically crude but are extremely effective at terrorizing civilians and forcing large number of people to flee a given area. If it does turn out that the regime is behind the latest attacks, it would definitely seem to fit a pattern.