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Chloropicrin and its alleged use in the Ukrainian war (Part 1)

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On 1 May, the United States formally accused Russia of using ‘the chemical weapon chloropicrin against Ukrainian forces in violation of the Chemical Weapons Convention (CWC)’. It added: ‘We make this determination in addition to our assessment that Russia has used riot control agents as a method of warfare in Ukraine, also in violation of the CWC. The use of such chemicals is not an isolated incident and is probably driven by Russian forces’ desire to dislodge Ukrainian forces from fortified positions and achieve tactical gains on the battlefield.’

Allegations of chemical weapons (CW) use first appeared after the start of the Russian-supported war in the Donbas in East Ukraine in 2014. Since the Russian full-scale invasion in 2022, CW claims have risen sharply. Most concern the use of lachrymatory agents (tear gas) such as CS and CN. The deployment of chloropicrin – an agent used in the First World War – would represent a significant qualitative escalation of chemical warfare. In contrast to CS and CN, chloropicrin cannot be used as a riot control agent (RCA) under the CWC. The US accusation, therefore, also implies that Russia did not declare, as required, and destroy all its CW. If proven, it would strikingly mirror Russia’s violation of the CWC with the novichok nerve agents used in assassination operations in 2018 and 2020.

This three-part blog contribution analyses the publicly available information about RCA and chloropicrin use in the Russo-Ukrainian war. The first part summarises the chemical warfare allegations between 2014 and 2024. Part 2 investigates the reports of chloropicrin use, and the final part discusses how the international community can address the CW allegations through action in the Organisation for the Prohibition of Chemical Weapons (OPCW).

Chemical warfare allegations in the Ukrainian war

The war in Ukraine began in February 2014 and led to Russia’s annexation of Crimea and the occupation of parts of the Donbas in the east of the country. On 24 February 2022, Moscow escalated the conflict by invading Ukraine from the north and northeast. After retreating in the face of stiff resistance and counterattacks, Russia concentrated its military power in the southeast. It succeeded in establishing a land link between the occupied Donbas parts and the Crimea. Following a major counteroffensive in the second half of 2022 and early 2023, the front essentially stalemated after the onset of spring.

Russia opened a string of local offensives at the end of 2023 and into 2024, gaining some tactical advantages in multiple places. They have not broken through the Ukrainian lines until now, but they impose pressure on the defenders. The current Russian incursion in the direction of Kharkiv in north-east Ukraine supports this objective. After many months of stagnating weapon supplies to Ukraine, significant arms shipments will resume by early June. Russian forces are consequently under immense time pressure to secure victories that will offer them future strategic advantages.

Static fortifications, trenches and other defences characterise the more than 1,000-kilometre frontline stretching from Kherson in the south-west to the Luhansk Oblast next to the border with Russia. These defences are layered in depth, making offensive operations very costly to the attacker. In April 1915, the German imperial forces needed a force multiplier to restore mobility to the front quickly. They had the answer in the form of chlorine clouds. More than a century later, we may again face a military situation where one side believes that toxic agents might be the key to a strategic breakthrough.

We have not yet reached a situation in which one of the belligerents has made use of lethal agents, like the sarin and chlorine attacks in Syria. Even so, RCAs typically utilised by police forces in domestic settings, such as the CN or CS, which have been reported in many allegations of use in the Ukrainian war, may offer advantages on a static battlefield. Land warfare (with limited or no aerial support) is essentially two-dimensional. Chemical agents, being heavier than air, make it three-dimensional because they will sink into trenches and seep into dugouts and underground resting places. They can also be effective in enclosed spaces. They force the defenders into the open, exposing them to bullets and shells. Their psychological impact on military personnel untrained in chemical defence may be enormous. They can thus seriously weaken the defensive lines.

However, there is the risk of escalation. RCAs lose much of their military utility in war once the defenders can protect themselves and receive the training to withstand impulsive reactions when confronted with them. It is a major concern about recent reports that Russian units may be deploying chloropicrin against the Ukrainians. In the First World War, chloropicrin was a gasmask breaker. It penetrated the existing charcoal filters and caused the wearer to vomit, forcing them to take off the mask while other toxic agents were poisoning the air. Today’s gas masks offer ample protection, but the agent is aggressive. Exposure may lead to acute skin irritation. Chloropicrin also implies the use of different types of delivery systems compared to standard RCAs.

The CWC bans any toxic chemical if its purpose is to develop or produce CW. It does not prohibit the possession and use of RCAs if intended for law enforcement or domestic riot control, provided their nature and the quantities are consistent with those purposes. If a toxic chemical is listed in one of the three schedules in the CWC Annex on Chemicals, it cannot be used for riot control.

Schedule 3 includes chloropicrin, meaning it was a past warfare agent but has significant commercial value today. If the allegations of chloropicrin use can be firmly established, Russia is in material breach of the CWC. It did not declare possession of these chloropicrin munitions as a CW and destroy the weapons.

Early accusations of RCA use

Allegations of chemical warfare or preparations for CW use first arose in 2014. Some of the earliest Russian claims date back to June and August 2014, even though some of the phraseology seemed to point to Ukrainian use of white phosphorus or other incendiary agents. During the battle for the Donetsk airport terminals in January 2015, Ukrainian sources asserted that Russian-backed militants were using a type of lachrymatory agent. However, the head of the self-proclaimed Donetsk People’s Republic, Alexander Zakharchenko, blamed Ukrainian troops for the chemical attacks, adding that there was a pungent smell after a shell burst, sulfur could be smelled, and it was impossible to breathe. A TASS correspondent at the site described how the agent made his eyes tear and caused him breathing difficulties.

A fighter of the Russian forces with K-51 grenades at the Donetsk airport. 2015. Source: Ukrainian Military Center (

In its public report of 20 January 2015, the Special Monitoring Mission (SMM) of the Organisation for Security and Cooperation in Europe recorded the condition of hospitalised soldiers reminiscent of exposure to a chemical warfare agent, possibly other than an RCA:

A Ukrainian soldier in a hospital in government-controlled Konstantinovka (56km north of Donetsk) told the SMM that he was being treated for injuries sustained at the Donetsk airport on 19 January. He said 80 Ukrainian soldiers in total had suffered the same injuries, manifested in uncontrollable muscle spasms, vomiting and difficulty breathing. Some, he said, had become unconscious. Eleven of the soldiers had been transferred to a hospital in Dnepropetrovsk, he said.

The first phase of the Russo-Ukrainian war ended with the signing of the second Minsk Agreement in February 2015, after which fighting subsided, and the warring parties settled in some form of trench warfare. Neither side seems to have alleged further CW incidents. Russia ramped up its ongoing disinformation campaigns in the months ahead of the Ukrainian presidential elections on 31 March 2019. Reports started circulating that Russian chemical warfare experts had been relocated from Syria to the Donbas amid detailed accusations of Ukrainian CW preparations, leading to concerns about Russian false flag operations.

The full-scale invasion of Ukraine

Within two to three weeks after the full-scale invasion of Ukraine on 22 February 2022, concerns about Russia unleashing chemical warfare mounted considerably. In the weeks before the offensives, Moscow had already launched a sustained disinformation campaign about so-called US-sponsored military-biological research activities in Ukraine, which eventually led to the convening of a Formal Consultative Meeting under the Biological and Toxin Weapons Convention in September and the rejection of a resolution Russia put the UN Security Council in November.

The tensions early in March 2022 were such that US President Joe Biden threatened a severe response if Russia resorted to chemical warfare (even though he did not go as far as drawing a red line). In March and April, Russian officials accused Ukraine of setting the stage for major incidents with toxic chemicals. They alleged that nationalists had mined storage facilities with ammonia and chlorine at the Sumykhimprom chemical plant to mass poison the inhabitants of the Sumy region if units of the Russian Armed Forces were to enter the city of Sumy. Two days later, on 21 March, Russian artillery targeted the plant and damaged a 50-tonne tank, as a consequence of which an ammonia cloud drifted towards the nearby location of Novoselytsya, forcing residents to close windows and take shelter. The leak was quickly repaired, and only one worker was reported injured. A spokesperson for the Russian Ministry of Defence made a similar claim on 6 April when accusing Ukrainian special services of having mined a warehouse holding 120 tonnes of chlorine at the Khimprom production association with the intent of blaming Russia for deliberately causing a chemical catastrophe that would kill locals. A week later, Ukraine accused Russia of using CW against the defenders of the encircled Black Sea town of Mariupol. However, the reports were vague and lacked much contextual detail. (An earlier blog posting, Prelude to chemical weapons use?, discusses those incidents.)

The mutual accusations continued for much of 2022. In mid-November, however, the Ukrainian charges became more specific when the Ukrainian State Border Service operating in the Donetsk region asserted that Russian-operated drones had dropped several K-51 grenades that disseminated a lachrymatory agent. The number of accusations also rose fast. At the end of 2023, Ukraine alleged 465 chemical attacks since the invasion in February 2022, including 80 incidents during December. Reports early in February 2024 cited the General Staff of the Armed Forces’ claim of 815 chemical attacks. A mere month later, the figure already passed the thousand mark.

K-51 grenade. Source: Ukrainian Military Center (URL:
RGR grenade. Source: Wikipedia Commons.

In a statement to the CWC Conference of the State Parties (CSP) under agenda Subitem 9d ‘Addressing the threat from chemical weapons use’ on 29 November 2023, Ambassador Oleksandr Karasevych identified the K-51 and RGR aerosol grenades as the RCA delivery systems. He added that no Ukrainian military formations were equipped with them. (Ukrainian units do utilise variants of those grenades with explosive charges.) He named the Russian manufacturers GNPP ‘Basalt’ and JSC ‘FNPC Research Institute of Applied Chemistry’. He also informed the CSP that the Security Service of Ukraine had initiated investigations into Russian CW use under Part 1 of Article 438 of the Criminal Code of Ukraine, ‘Violation of the laws and customs of war’.

At the 105th session of the OPCW Executive Council (5-8 March 2024), Ukraine provided further details about the alleged attacks:

As of March 01, 2024, information on 1060 cases of the use of chemicals by the Russian Federation is investigated, as of which 72 facts have been verified due to active hostilities.

According to the conclusion of the Chief of the Chemical and Biological Defence Troops of the Support Forces Command of the Armed Forces of Ukraine, the means of delivery of munitions equipped with hazardous chemical agents are UAVs (74%), artillery (13%), grenade launchers (1%) and other (12%). The types of ammunition that are armed with hazardous substances are K-51 (71%), gas (17%), VOG (11%) and liquid (1%). Most of the munitions were used during the daytime (93%), and at night (7%).

As of February 2024, 946 cases of medical care for Ukrainian servicemen with poisoning by an unknown substance that occurred in the areas of hostilities were registered in Ukrainian healthcare facilities.

Russia denies all CW use and points to the fact that it completed the destruction of all its declared CW under OPCW supervision in September 2017. It counters the accusations with its own allegations of chemical crimes committed by Kyiv nationalists.


Part 2: Allegations of chloropicrin use

Part 3: International responses to alleged CW use in Ukraine

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