In terms of raw casualty numbers, Tuesday's apparent nerve gas attack near the Syrian city of Khan Sheikhoun — believed to have killed at least 70 — should hardly be significant against the backdrop of a war that has left hundreds of thousands of people dead.
But that was never the point of chemical weapons. Since European powers first used them over a century ago at the height of World War I they have held a psychological and political shock value in many ways out of proportion to their physical or military effect. Alongside the threat of biological warfare, they hold a very distinct horror.
In the trenches of World War I, doctors noted that the paralyzing fear of a gas attack often exceeded that of conventional artillery and bombs, even though the latter killed many more people. By the end of that conflict, basic gas masks and chemical protection equipment meant many soldiers could survive such an attack relatively unscathed.