Speculation that Russian President Vladimir Putin has or will use chemical weapons in Ukraine is growing. Russia’s efforts to block punishment for Syria’s use of chemical weapons confirms Putin’s sympathy for the weapons. And the Kremlin’s allegations of US chemical and biological weapons labs in Ukraine may end up serving as a pretense for Russia to use chemical weapons.

What is known about the intentions and capabilities of Russia to use chemical agents in Ukraine?

First, Putin has not used chemical weapons on the battlefield against Ukrainian soldiers and citizens. But he is increasingly likely to do so as he grows more desperate for military victory and as Russian forces are pushed back. History includes numerous examples of leaders resorting to chemical weapons to defeat urban foes, including Spain against Berber tribes in the 1920s, Italy against Ethiopia in the 1930s, and Iraq against Kurdish groups in the 1980s. There have been reports of the use of white phosphorus in Kramatorsk, but it should be noted that this is not a chemical but an incendiary weapon. It is not accounted for in the Chemical Weapons Convention, the landmark treaty that prohibits the use of chemical agents. There are also allegations that members of the delegation attending the peace talks between Ukraine and Russia on March 3–4, 2022 experienced symptoms consistent with poisoning.

Second, if Russia uses chemical weapons, the primary purpose will be to inflict psychological injury on Ukrainians, more so than to inflict a large number of casualties. The widespread use of chemical weapons during World War I and the subsequent use in colonial and contemporary civil wars underlines that the absolute effectiveness of such agents in terms of casualties and destruction is limited. Although chemical weapons can be useful among rubble where bombs and bullets cannot, they have limited military effectiveness as a battlefield weapon. They are vastly susceptible to weather conditions, areas’ topography, and opponents’ protective gear. Instead, they tend to be used as a strategic magnifier and supplement to other military tools. If Russia uses chemical weapons, it will also continue to use conventional weapons for physical destruction. Chemical weapons are an add-on to spread fear, confusion, and uncertainty in order to damage Ukrainian morale. The deliberate Russian strategy of targeting civilians, as seen in the horrific footage from Bucha, would continue.

Third, Russia has chemical weapons, but the size of their stockpile is unknown. In 2017, the Organization for the Prohibition of Chemical Weapons (OPCW) confirmed that Russia had destroyed its stockpiles of blister and nerve agents, which had been declared to the OPCW in 1997. However, Russia deployed Novichok and other chemical agents on opposition leader Alexei Navalny, Bulgarian arms dealer Emilian Gebrev, founder of Rosbiznesbank Ivan Kivelidi, and former Russian military intelligence officer Sergei Skripal, among others. Based on the historic use of nerve agents, this suggests that Russia keeps a stockpile of Novichok agents.

Chemical weapons expert Dan Kaszeta suggests that chlorine and ammonia are most likely to be used as they can be blamed on Ukraine in a false flag operation. But there is little verified information on the true Russian array of chemical weapons. The Russian program has been marked by secrecy, defiance of international treaties, and denial. Regardless of how much Russia possesses, experts suggest that it can make hundreds of kilograms of chemical agents within a matter of weeks.

Fourth, the international community will respond swiftly and impose additional severe punishments on Russia if and when it uses chemical weapons. Social scientists have found that the international community responds more swiftly to chemical weapons attacks when the victims are from Western countries rather than from developing countries. Hence, there were largely ineffective and inconsistent third-party reactions to Syrian President Bashar al-Assad’s chemical weapons use during the civil war from 2011 to 2018 in contrast to the attempted poisoning of Skripal and his daughter Yulia on British ground. The White House has already assembled an international team to discuss NATO’s response to Russian use of weapons of mass destruction, including chemical weapons. No official statement has been made on the specifics of what a response would look like, but we can expect it to be a strong one.

While President Biden has reiterated that he will not send American troops to battle Russian forces, NATO might choose to expel Russian diplomats, remove Russia from the G20 and the United Nations Human Rights Council, suspend Russian officials from participating in the General Assembly, maintain economic pressure, end European purchase of Russian energy (extremely difficult), or increase cyberattacks on Russian governmental bodies. Removing Russia from the UN Security Council would be nearly impossible mostly due to China’s veto power. President Biden and other leaders will be hesitant to use conventional military force against targets such as chemical weapons laboratories and military bases due to the fear of escalation and drawing NATO into a direct conflict with Russian nuclear retaliation. However, the likelihood of a military response would significantly increase if chemical clouds drift over borders.

Fifth, the United States can respond with nuclear weapons according to its nuclear posture released by the Trump administration. Under President Donald Trump’s nuclear posture review (NPR), nuclear weapons can be used to deter and respond to “significant non-nuclear strategic attacks” on the United States or allies. The Biden administration’s long-awaited NPR will follow a similar posture, merely adjusting the language to use nuclear weapons in “extreme circumstances”. However, it is unlikely that President Biden will use nuclear weapons in response to chemical weapons because he has long supported a policy of using nuclear weapons for the sole purpose of deterring a nuclear threat, and, if necessary, to retaliate against one. Although his new NPR will not include a sole purpose policy, the international norm that nuclear weapons should not be used in response to chemical weapons is likely to persist.

While the international team meets to discuss responses to Russian chemical weapons use, NATO should prioritize the provision of protection equipment—which the United States has started—and crisis management and decontamination teams to Ukraine. Instead of focusing the discussion on what the West’s reaction should be, the international community should prepare for Russian discriminatory acts in order to save as many Ukrainian lives as possible and thwart a nationwide panic.

Doreen Horschig is a Stanton Nuclear Security Postdoctoral Fellow at MIT’s Security Studies Program.