The first agreement to ban chemical weapons came in 1675. (France and the Holy Roman Empire forswore poisoned musket balls.)
Three centuries and at least six international treaties later, they are still being employed, and there’s little the world can do to stop it.
VX nerve agent was used in the February 13 murder of Kim Jong Nam, the half-brother of North Korean leader Kim Jong Un.
In Syria, the regime of President Bashar al-Assad has repeatedly used chlorine as a weapon against its own people, even after it agreed to surrender the country’s chemical munitions following a 2013 sarin gas attack that killed hundreds of civilians in a Damascus suburb.
What appeared to be a gas attack delivered by warplanes killed at least 58 people in Syria’s Idlib this week, drawing another round of international condemnation. The United Nations was already considering new sanctions on Syria for chemical attacks in its six-year civil war.
A report from weapons inspectors in October concluded that the Syrian military had carried out attacks using barrel bombs filled with chlorine in 2014 and 2015, even though Assad’s forces denied it.
Another study in August detected the presence of previously undeclared chemical agents at several sites, adding to concerns the regime lied about the extent of its program.
Other attacks have been documented by independent groups, including a suspected mustard gas attack by Islamic State in northern Iraq in 2016. Chlorine has various industrial uses, and can also be used as a choking agent that burns the lungs.
The UN Security Council adopted a resolution in 2015 that puts chlorine in the same category as other agents. Syria didn’t include chlorine as part of its disclosure of chemical weapons production and storage sites, which it surrendered after the threat of US — led military action.
Syria’s stash included about 1,300 metric tons of VX, sarin and mustard gas and was said by Western states to have been among the largest stocks in the world. North Korea still has one of the biggest stockpiles of chemical weapons.
Despite international treaties signed before the outbreak of World War I, Germany used poison gas on the Western Front in 1915. Everyone else joined in, leaving more than 90,000 dead and a million wounded in chemical attacks by the war’s end.
That memory, and the 1925 Geneva protocol, deterred the use of chemical and still-more ghastly biological agents on the battlefields of the Second World War and most conflicts since then.
Even so, Saddam Hussein’s chemical attacks killed 5,000 Iraqi Kurds in 1988, while a sarin attack by the Aum Shinrikyo cult killed 13 people on the Tokyo subway in 1995.
And while the latest treaty, the 1997 Chemical Weapons Convention, has been signed by 192 nations, the holdouts include North Korea, Egypt and the newly independent South Sudan. Israel has signed but not ratified.
The power of chemical weapons in the public imagination was illustrated by the award of the 2013 Nobel Peace Prize to the Organisation for the Prohibition of Chemical Weapons, which destroyed Syria’s declared stockpile on behalf of the UN.
The US and Russia are still scrapping their own chemical weapons stores, in accordance with promises they made two decades ago.
Almost everyone agrees on the need to ban chemical munitions — even Syria finally accepted the Chemical Weapons Convention under pressure. But they can’t agree on how to do it.
The assassination of North Korea’s Kim in public has highlighted the danger. After the 2013 sarin attack, Russia and China didn’t want to sanction armed force in Syria, while other UN Security Council members such as the US and France argued for a military response.
Russia labelled it an excuse for the US to topple regimes like Assad’s, just like the invasion of Iraq in 2003.
The proponents of a strike say the failure to follow through with an attack has weakened deterrence.
Intelligence officials have raised concerns that Islamic State is training its foreign fighters in the use of chlorine gas as a terror weapon that could be used when they return home.