For the past few months, Syrian forces have been trying to take control of Eastern Ghouta, an opposition-controlled city outside the capital of Damascus that is densely populated.

The fighting has been fierce, but the forces of President Bashar al-Assad have made huge advances against rebel forces. All that was left of the opposition-controlled territory in Eastern Ghouta was a small district called Douma.

Over the weekend, Syrian regime forces decided to finish the job by conducting an attack using chemical weapons in Douma.

According to media reports, 42 people were killed and more than 300 were wounded—many of the victims being children. The video footage emerging from the attack is heartbreaking. Of course, Russia denied that chemical weapons were used.

Soon after the attack, the opposition fighters in Douma agreed to a cease-fire in exchange for safe passage to other opposition-controlled territory in Syria. The capture of Eastern Ghouta marks the biggest military victory for Assad since he captured Aleppo in 2016.

On twitter, President Donald Trump called out Russia and Iran’s complicity in the Douma chemical weapons attack and suggested there would be a “big price” to pay. 

Adding confusion to the situation, the Israeli air force conducted a limited airstrike against Syria’s T4 air base near the city of Homs during the early hours of April 9. T4 air base is home to Iranian, Hezbollah, and Russian forces.

It is not clear what Israel’s motive was, but this is the second time in a year that Israel has attacked this particular air base. It is reported that Iranians were killed in the strike, but no Russians.

While the Pentagon denied U.S. involvement in the Israeli strike, a quick response to the chemical attack is expected from the U.S.

Unlike his dithering predecessor, Trump has proven to be decisive on issues regarding Assad’s chemical weapons.

On April 4, 2017, Assad killed 100 people and wounded hundreds more using chemical weapons in Khan Shaykhun, a town in northeastern Syria. Only three days later, the Trump administration launched a blistering cruise missile attack on Shayrat Airbase—the location from where the chemical weapons attack had originated.

There is little doubt that U.S. military planners are preparing new options for the president to approve.

Like last year’s strike, the U.S. military response against the Assad regime must be punitive, decisive, and directly linked to the illegal use of chemical weapons against civilians. Every effort must be made to degrade Syria’s ability to launch similar chemical weapons attacks in the future. A message must be sent that there is a high price to pay for the use of illegal chemical weapons, especially against civilians.

Unlike last year’s strike, though, the U.S. should lead an international effort this time. It is not right that the international community voices concern about the illegal use of chemical weapons but then stands merely as a bystander when it is time to act.

A joint international response will send an important international message while also allowing the burden of response to be shared.

The United Kingdom, France, Germany, Italy, Spain, Turkey, Saudi Arabia, United Arab Emirates, and Qatar all operate some variant of cruise missiles, for example. The Arab world in particular should take more responsibility for its region and work alongside the U.S. during any punitive strike against Syria.

The Europeans need to step up to the plate, too.

French President Emmanuel Macron and Trump agreed over the weekend to a “strong, joint response.” In the past, Macron had declared Syria’s use of chemical weapons a “red line.”

The U.K. is still haunted by the 2013 vote in the House of Commons that barred a strike on Assad after the infamous chemical weapons attack in Ghouta. But since 2013, the public mood has changed. Prime Minister Theresa May should lead an international effort against the use of chemical weapons in Syria with the same vigor she has displayed in condemning the recent use of chemical weapons in Salisbury.

This latest attack makes yet another mockery of the Obama administration’s claim that Syria got rid of all its chemical weapons in 2013.

In 2014, then-Secretary of State John Kerry boasted that in Syria, “we struck a deal where we got 100 percent of the chemical weapons out.”

Regrettably, President Barack Obama’s naiveté, combined with his failure to enforce his own red line in 2013 over the use of chemical weapons, planted the seed for this most recent attack.

As with much of the Obama administration’s foreign policy, the Trump administration is left picking up the pieces. This chemical weapons attack in Douma is merely the latest example. Tragically, it is unlikely to be the last.