Last Tuesday, a Danish ship offloaded a cargo of chemicals in the UK. There is nothing remarkable about the ship, or even the cargo, which is similar to the industrial chemicals regularly handled, transported and destroyed at British facilities on a routine basis. What is remarkable is where they came from and how they ended up in the UK, for these chemicals were once ingredients for Syrian President Bashar Al Assad’s secret chemical weapons program—a program that he used against his own population.

As Syria descended into civil war, videos and reports started to surface on social media claiming that Assad was using chemical weapons. On both sides of the Atlantic, intelligence agencies worked to assess these reports. The UK pressed for an investigation, and a team of international inspectors travelled to Syria. Along with our U.S. colleagues, we started quietly planning how we would respond if the reports turned out to be true.

Matters came to a head in August 2013, when Assad brazenly launched a chemical weapons attack outside Damascus, killing nearly 1,500 civilians, including at least 426 children.

It was clear that the international community had to act. Following a deal between the U.S. and Russia, an unprecedented global effort began to remove the Syrian regime’s chemical weapon stockpile. A tall order in the middle of a warzone, made even more difficult by an obstructionist Syrian regime. By late last month, all of Assad’s declared chemical stockpile had been removed from Syria.

The effort has involved contributions from many nations, including the United States, Denmark, Norway, Italy, Finland, Germany, Russia and China. The UK contributed over $3 million to fund the operation and has played an integral part in its completion.

When Danish and Norwegian ships collected the declared chemicals from Syria, we provided a military escort.

When the U.S. ship destroying the most dangerous chemicals needed to get them out of their containers and into their destruction equipment, we provided specialised gear for the job.

And when we discovered that some 200 tons of chemicals could be more efficiently disposed of at specialist facilities than at sea, we offered to take them and destroy them ourselves. These chemicals recently arrived in the UK, and will be destroyed over the coming weeks.

The removal and destruction of these weapons meaningfully reduces Assad’s ability to terrorise the Syrian people. The operation also represents a considerable achievement for the global community. It required an unprecedented level of international cooperation, and it marks a major step towards the elimination of chemical weapons worldwide.

Our work is not yet done.  Syria’s obligations do not end with the chemical destruction. For example, the Chemical Weapons Convention Assad has now signed requires him to destroy his chemical weapons facilities as well. We must ensure that he honours those obligations. We must also continue to investigate serious concerns about whether Assad declared his entire stockpile.

Nor, as we maintain our focus on eliminating chemical weapons, can we forget that the Syrian regime remains responsible for the civil war that continues to rage, with appalling human costs: 10.8 million people are in dire need of humanitarian aid, 2.9 million have been forced to flee Syria, and 170 thousand people have died. It is the world’s worst humanitarian crisis.

On July 14, the UN Security Council unanimously voted to authorize the UN to use four additional border crossings to deliver life-saving humanitarian aid to some of Syria’s least accessible areas. The resolution forbids the Syrian regime from obstructing, impeding or delaying the convoys, as they have done repeatedly in the past. As a result, an additional 1.3 million people will have aid. 

That is another step forward for the international community, but we must never take our eyes off the ultimate goal. Despite a tumultuous foreign policy landscape, particularly in Ukraine and Gaza, resolving the Syrian crisis remains a top priority for the British government. Lasting peace will only come with a negotiated settlement achieved through a Syrian-led political transition that truly reflects the wishes of the Syrian people.

Westmacott is UK ambassador to the United States.