In the scale and quality of the war in Syria it was a small act, of perhaps half a dozen missiles aimed, or detonated, in a residential area of a city which was fighting the forces of Bashar al-Assad.
In a war which has seen nearly two million people flee their own country, trying to escape the risk of death which has already claimed more than 100,000 of their fellow citizens, this does not seem a large incident.
This is especially so, given the litany of atrocities that seem to be reported on an almost daily basis. The execution of prisoners, the killings of civilians, torture, rape, and the defiling of the dead have all been recorded. Landmines, cluster bombs and high explosives have been delivered by both air and car.
Large sections of world heritage have been wiped from the map. Against all of these calamities, the deaths of a few hundred more people do not seem that important.
This view is mistaken. If second-generation chemical weapons are being used in Syria with the intention of killing civilians then we have just reached a new level of barbarism for humanity. Although our species has a long history with the use of poison as a method of killing, the industrialisation of this to chemical weapons is an invention of the 20th century.
In the last century, we developed two generations of chemical weapons. The first generation involved choking gases, such as chlorine. Mustard gas is the classic example in this bracket. By the end of World War I, 126,000 tonnes of chemical agents had been fired into opposing armies.
More than one million of these men, including Adolf Hitler who was temporarily blinded while serving in the trenches, would be affected by late 1918. Hitler was one of the lucky ones who was not killed in the battle or died an agonising death over the following decade.
It was the inhumane nature of this weapon that lead to the international community banning their use in warfare in 1925.
The remarkable thing about the 1925 convention was that it held during World War II. The ultimate fear before this conflict was that poison gas would rain out of the heavens on to terrified civilians below. Yet even though all sides had amassed large amounts of these weapons, everyone avoided the use of them. Even Hitler realised there were limits to what could be done during times of war.
This meant that the ultimate fear never came to fruition. Hitler's restraint with using gas to kill people only went that far. He had no such compunctions with the use of the last of the first-generation chemicals, Zyklon B, which was pumped into gas chambers to help the Holocaust to collect its genocide of millions.
Saddam Hussein was the last leader to use the first generation of chemical weapons. He used these on the battlefield against Iran and against his own dissident citizens, killing thousands.
World War II and the attacks by Hussein could have been worse if second-generation chemical weapons had been used in either conflict. These are the nerve agents such as tabun, sarin and VX. They are designed to be absorbed into the body through the skin, airways or mouth.
Once in the body they disrupt the function of the nervous system and loss of control of bodily function follows. Vomiting, drooling, urinating, defecating, loss of all reflexes and then lapsing into a coma. Suffocation, as a result of convulsive spasms, ends the existence for the victim. There is nothing quick, nor dignified, in this type of death.
I do not imagine it's possible to understand the pain that a witness would feel, watching someone they loved expire like this. Saddam Hussein wanted to use these chemicals, but found them too difficult to weaponise. It appears that someone in Syria has now crossed that boundary, and deployed second-generation chemical weapons against a civilian population.
In addition to being inhumane, these weapons are also extremely indiscriminate. It is their inability to be carefully targeted which makes them classified as a weapon of mass destruction. Estimates suggest their impact is in the range of 20 civilian casualties for every soldier killed.
If the evidence emerging from Damascus is accurate, this figure may be correct as the death toll appears to be disproportionately made up of children, women and other non-combatants.
It was the inhumane and indiscriminate nature of these weapons that lead to an enhanced internationally agreed ban on the production, storage or use of them in 1993. In 1998, their use was recognised as a war crime by the International Criminal Court.
We do not have similar prohibitions on either biological or nuclear weapons. These prohibitions are the strongest rules international law has to offer in the control of weapons of mass destruction, and they make up the line that President Barack Obama warned Assad last year not to cross.
If this line has been crossed, Syria, international law, and humanity in general has fallen to depths that previous generations had avoided. If this has happened, Obama must follow up his rhetoric or he will be viewed as weak.
If Obama does not act as he threatened, whoever used these weapons will feel free to continue to escalate the use of them, acting with impunity.
If so, this nightmare is only just beginning. If not, the deaths of a few hundred people may be the turning point of the entire conflict.
Alexander Gillespie is Professor of Law at Waikato University and author of A History of the Laws of War (Oxford).