Among Donald Trump’s first acts as president was to abandon Barack Obama’s craven and ultimately failed efforts to avoid entanglement in the Syrian civil war. Hours after the revelation that Damascus had once again used a complex nerve agent on a civilian population, Trump did not vent shallow bluster all over Twitter. Nor did he drag out the process of a retaliatory response over the course of weeks involving an endless parade of spineless and compromised European bureaucrats. He ordered cruise missile strikes and, though calibrated to produce minimum casualties, it established a measure of deterrence that held for a time.

But deterrence requires constant maintenance, and Donald Trump has proven in the months that have elapsed since that strike on a Syrian airbase in April of 2017 that his heart isn’t in it.

In 2018, Damascus again executed an unconventional attack on a civilian target using what was believed to be a non-chlorine chemical agent. Trump again promised a response, but deliberations dragged on for days. Eventually, the Pentagon mounted a “proportionate” strike on two Syrian targets—not the disproportionate attack on Syria’s air force and chemical-weapons facilities some advocates had sought. And while the week that elapsed between the chemical attack and the retaliatory response allowed Trump time enough to coordinate with America’s allies in France and the U.K., it was also long enough for Syrian forces to neutralize the rebel forces and retake the territory they targeted. In the end, Assad suffered a bloody nose, but his use of chemical weapons achieved strategic objectives.

The new efficacy of chemical weapons on the battlefield extends beyond Syria. Complex nerve agents seem to be the new weapon of first use for rogue regimes looking to execute acts of terrorism abroad. What’s more, this White House seems intent on rewarding that behavior.

In February of 2017, the North Korean regime sponsored the assassination of Kim Jong-un’s half-brother using VX nerve agent, something the United Nations classifies as a weapon of mass destruction, in a populated airport in Malaysia. Sixteen months later, the president of the United States sat down with the man who likely approved of that operation. Demanding accountability for that attack wasn’t on the agenda.

Similarly, in March, a former Russian military intelligence officer and his daughter were poisoned by the tightly controlled nerve agent of Russian origin, Novichok, in the English city of Salisbury. British Prime Minister Theresa May blamed the Putin regime, and her substantive claims were supported by NATO, the European Union, and the United States. But just four months later, Trump would sit down with Vladimir Putin and hold a slavish press conference alongside the Russian leader. As far as we know, the attack on Salisbury never came up.

The message is clear: If you’re the outlaw leader of a revisionist state and you want a legitimizing sit-down meeting with the most powerful man in the world, gas some civilians.

Republicans are quick to note that the Trump administration has demonstrated more commitment to containing Moscow’s aggression than any of its post-Cold War predecessors. That fact is beyond debate, though it says less about this administration’s policies than it does about the last three administration’s naiveté with regard to Russia’s revanchist regime. And yet, the Trump administration’s record is hardly blemish-free when it comes to deterring Russian aggression. According to the letter sent to the White House by House Foreign Affairs Committee Chairman Ed Royce, the Trump administration has been derelict in enforcing sanctions against the Russian government as a response to the event in Salisbury.

It is incumbent on the Trump administration to succeed where Obama failed and reestablish the prohibitions around the use of chemical weapons that were put in place after the First World War and remained inviolable for nearly a century. It is failing in that charge. If the use of chemical warfare becomes the new status quo of the 21st Century, it will be a deeply regrettable one. And we will not be spared its terror.