As vice president in 2011, Joe Biden had a front-row seat to one of the great foreign policy blunders of the Obama administration: the unilateral withdrawal of all US troops from Iraq. President Obama acted despite warnings that a pullout would leave a vacuum the region’s most malign forces would exploit. Those warnings were borne out, as the fanatical jihadists of ISIS swept into the region and unleashed their reign of terror.

Instead of learning from Obama’s debacle, Biden replicated it. As president in 2021, he ordered all remaining US troops in Afghanistan to depart. Again the president disregarded warnings that the results would be calamitous. Again the warnings proved accurate. Kabul swiftly fell to the Taliban, which unleashed barbarism, repression, and the subjugation of girls and women across the country.

Three years later, Biden once more finds himself facing a situation eerily similar to one faced by Obama.

The Telegraph reported on April 6 that Russia is carrying out illegal chemical attacks on Ukrainian troops. On a near daily basis, it found, Moscow is deploying drones with gas grenades against Ukrainian soldiers in embedded positions. Typically the grenades are loaded with CS, a form of tear gas, but The Telegraph’s sources say they sometimes contain chlorine, chloropicrin, or hydrogen cyanide — all substances used as chemical weapons in World War I.

“Nearly every position in our area of the front was getting one or two gas grenades dropped on them a day,” a Ukrainian commander told the Telegraph. The chemicals cause intense burning in the eyes, throat, lungs, and skin and can prevent breathing and swallowing. When the grenades detonate, the pain and asphyxiation force Ukrainian troops into the open, where they can then be cut down with artillery. These attacks are flatly banned in warfare under the Chemical Weapons Convention.

Russia’s tactics recall the deadly gas attack by Syrian dictator Bashar al-Assad on a rebel-held neighborhood near Damascus in August 2013. Obama had said explicitly a year earlier that any use of chemical weapons by Assad would be a “red line” that would “change my calculus” on US involvement in the Syrian civil war. But when that red line was crossed, Obama blinked. Then-secretary of state John Kerry would later admit that Obama’s failure to act “cost us significantly” and broadcast a message of American weakness. Damascus gloated over the “historic American retreat.” Other regimes took note. Six months later, Vladimir Putin invaded Crimea — a foretaste of the war he would launch in 2022 to wipe out Ukrainian independence.

Soon after that war began, Biden drew his own red line.

In March 2022 he was asked what America and NATO would do if Putin used chemical weapons against Ukraine. “It would trigger a response,” he promptly answered. “We would respond. We would respond if he uses it.”

So Biden again faces a choice: Will he live up to his pledge not to tolerate any use of chemical weapons — or will he follow Obama’s disastrous playbook and let Putin get away with gassing Ukrainians?

The stakes are huge, wrote Hamish de Bretton-Gordon, the former commander of NATO’s Combined Joint Chemical, Biological, Radiological, and Nuclear Defense Task Force, in a Telegraph op-ed Monday. The alliance is on notice that “no weapons are off limits” for Putin and “escalation in the use of these weapons is highly likely.” It is imperative, he said, that the West “show some steel and force Putin to back down.”

The most significant step the allies could take is to formally invite Ukraine to join NATO. No nation in modern times has demonstrated as much loyalty to the West as Ukraine. Confirming Ukraine as a permanent NATO ally, a status Kyiv has amply shown it deserves, would decisively signal to Putin that his bid to conquer Ukraine will not be allowed to succeed.

With Congress back in session, Biden ought to pull out the stops to finally get the House to enact the Senate-passed Ukraine military aid package. That would mean setting partisanship aside and giving House Speaker Mike Johnson the political support he needs to force the measure through, assuring him that Democrats will not then join the anti-Ukraine MAGA faction and depose him.

Biden also has authority to sharpen sanctions against Russia. He could target the network of companies linked to Russia’s state-owned nuclear corporation — a key element of the Kremlin’s war machine, which has so far gone unsanctioned. He could weaken Russia’s war effort in Ukraine indirectly, by countering (and thereby raising the cost of) Russian operations elsewhere, including in Moldova and the Balkans.

Whatever happens, Biden dare not repeat Obama’s error. This time, the chemical weapons red line must be defended.