Zombie movies like World War Z and Army of the Dead are no doubt terrifyingly interesting— hordes of the undead chasing the living while their bodies rot away. Bonus if they’re mindlessly chanting, “Brainssss. Brainssss.” It’s pretty wild. During World War I, there was a battle known as the “The Attack of the Dead Men,” which could be the closest zombie experience that humanity had.

The story didn’t happen in some post-apocalyptic setting, kind of. It was during the battle at the Osowiec Fortress in 1915 between the Germans and the Russians.

The Era of Poison Gas

If you haven’t heard, World War I was an age of poison gas. Different vapors of death were invented and utilized to attack enemy troops: phosgene gas, mustard gas, chlorine gas (which US troops thought could be combatted by wearing masks with urine). They were all nasty in their own destructive ways.

The Gas Attack

So the Russians were protecting the Osowiec Fortress when the Germans decided it was time to launch a full-frontal offense by using 14 battalions of infantry, including sappers, siege guns, and some 30 batteries of artillery using shells filled with chlorine gas. If you haven’t heard, exposure to chlorine gas could cause fluids in the lungs, causing the victims to drown from the inside. The Germans made sure the wind was to their advantage to make sure that the gas would reach the adversaries, you know, instead of backfiring if the wind changed direction. Luckily for them, the god of the wind was in favor of them.

The 12 kilometers wide and 12 meters high smoke of death reached the Russians, who didn’t have any sort of protection that could shield them from inhaling chlorine gas aside from their wet rags. The Germans were not done, as their full-frontal offense also included open-firing the fortress. Some 1,600 Russians almost instantly died.

The chlorine and the water in the air turned the chlorine into hydrochloric acid. As we know, hydrochloric acid is a form of strong chemical that’s also known as muriatic acid. It dissolved the Russians from inside out because of the water in their lungs. Soon enough, the skin on their faces began to melt away, too. If that’s not horrible, I don’t know what is.

A Surprise in the Fortress

The Germans pushed forward, expecting little to no resistance from the fortress defenders. They were shocked when an army of bloody and melting Russians counter-attacked. This in turn threw the Germans into a state of sheer terror and they bolted back for their own lines. According to Russia Beyond, “Sixty men opened fire with their faces wrapped in bloody clothes, trembling and coughing, literally spitting out pieces of their lungs onto their bloodstained shirts. Although exhausted and poisoned, they advanced with the sole purpose of crushing the Germans.” In their headlong retreat back to their own lines, quite a few Germans got tangled up in their own barbed wire and were bayoneted by these “dead” zombie soldiers coming at them.

Despite such desperate bravery shown by Russian troops in their last minutes alive, they still had to demolish the Osowiec Fortress later on so that it wouldn’t fall into the hands of the Germans.