The horrors of the First World War must be recalled as we grapple with today’s security challenges. Many years after it ended, one Canadian soldier described the chlorine gas attack at the Second Battle of Ypres, describing how the green gas “came up and went over the trenches – and it stayed.” On this solemn anniversary, we remember the atrocities with the resolve to make sure that unlike that gas, the threats do not linger.

The events one hundred years ago in Ypres marked a watershed moment: the first time that chemical weapons had been deployed on a large scale in battle. This helped to prompt the 1925 Geneva Protocol, which banned the use of chemical weapons outright. Some seventy years later, the Chemical Weapons Convention prohibited the development, production, acquisition, stockpiling, retention, transfer and use of chemical weapons. It also required States Parties to destroy any chemical weapons they owned or possessed.

The Geneva Protocol and the Chemical Weapons Convention are accepted as an indispensable part of the international norm against chemical weapons. The international community can be proud of this significant achievement.

At the same time, we owe it to the victims of chemical weapons over the past 100 years – and future generations at risk of attacks –to remember that the world is not free from this threat.

Less than two years ago, confirmation of the use of chemical weapons in Syria served as a shocking reminder that these indiscriminate arms have not yet been consigned to history. Allegations of the use of chemical weapons continue. That some of these allegations surround the use of chlorine gas is a bitter irony and a reminder that the international community cannot be complacent about its achievements, nor can it allow the taboo that surrounds such weapons to fade.

The multinational effort to eliminate the chemical weapons programme of Syria was a momentous undertaking and an important achievement. It reaffirmed international resolve against chemical weapons, and it illustrated the power of collective action in the service of a common goal.

The only fitting tribute to the memory of those who died at Ypres, and to all victims of chemical warfare, is to rid the world of chemical weapons once and for all.

On this solemn anniversary, let us recommit to this life-saving goal.