Ukrainian soldiers say Russian drones are dropping tear gas on the front lines, choking troops and starting fires in the trenches

• Ukrainian troops recount horrifying experiences with tear gas on the battlefield.
• They told CNN Russian drones were dropping the chemical agent in trenches.

Ukrainian soldiers battling in front-line trenches say they are facing a terrifying threat from Russian drones: CS gas, also known as tear gas, leaving troops fighting for breath as fires start around them.

The chemical agent, which causes chaos and panic before artillery follows, paints a bleak picture of the kind of fighting happening as winter settles in and Russia presses Ukrainian defenses.

Ukrainian troops stationed along the front told CNN about their experiences, reporting a recent surge in the use of tear gas, which is purportedly being dropped by Russian drones into trenches. At least nine chemical attacks have bene reported, and there has been at least one fatality.

Two Ukrainian service members affected by the gas gave a horrifyingly detailed account of the experience.

"At first I saw smoke," one said. "We ran out from the trench and the gas suddenly caught fire. The trench was in flames. This gas burns, blinds you, you can't breathe, shoots down your throat immediately. We didn't even have a second."

The use of tear gas — a flammable chemical agent which can cause severe eye, respiratory, and skin irritation and, in particularly high concentrations, permanent injuries and death — has been documented in past wars, but its use in warfare, along with other riot control agents, is prohibited under the United Nations' Chemical Weapons Convention. There have been other documented cases of Russia using tear gas on the battlefield, and Russia has been accused of a laundry list of war crimes.

Ukrainian naval forces, for instance, accused Russia around this time last year of using drones to drop grenades believed to contain chloropicrin, another chemical irritant, and similar allegations were made back in May.

The alleged use of chemical agents further highlights Russia's brutal way of war, much like the "human wave" tactics employed around Avdiivka and in other sectors of the front lines. That strategy involves troops throwing themselves at the front. The approach stresses Ukrainian defenses and exposes vulnerabilities but also results in high losses and significant carnage.

There have also been reports of Russians taking amphetamines to lower their inhibitions during combat or block pain and hard drugs to stave off boredom, which has resulted in some troops returning home with serious addictions, and Russia is also reportedly sending amputees and other injured troops back into battle as casualties mount.