On August 6, 1915, during World War I, German forces launched a chlorine gas attack against Osowiec Fortress, expecting the toxic cloud to overwhelm the Russian defenders and clear the way for capture. The gas spread through the fort, causing severe respiratory distress, temporary blindness, and chaos among those inside.
Assuming the garrison had been wiped out, German infantry advanced—only to encounter a startling scene. From the lingering haze emerged Russian soldiers, many gravely injured, their faces wrapped in blood-soaked cloth and their bodies weakened by the poison gas. Despite their condition, they moved forward with fixed bayonets, launching a determined counterattack.
The sight of these badly wounded yet advancing troops shocked the German forces, who broke ranks and retreated. This event, later known as the Attack of the Dead Men, became one of the most haunting episodes of the war. Though many of the defenders later died from their injuries, their resistance transformed what seemed like certain defeat into a powerful symbol of courage and determination.
Chemical warfare during World War I
Chemical warfare made its debut on the battlefield during the onset of the Second Battle of Ypres during the First World War. The engagement was fought for control of a crucial strategic area, and the Germans were determined to secure victory, even if it meant resorting to the use of a perilous and somewhat uncontrollable weapon.
At around 5:00 PM on April 22, 1915, German soldiers unleashed canisters containing a deadly mixture of poison gases, bromine and chlorine. The noxious fumes drifted across the battlefield toward the Allied line, compelling two colonial French divisions to abandon their positions in a desperate attempt to escape the lethal vapor. With no specialized equipment to counter the attack, troops were forced to fashion makeshift respirators from linen.
As a result of this battle, the British withdrew to a new defensive line. Soon after, poison gas became a familiar presence on the Western Front, despite being deemed a war crime under both the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare. Both sides resorted to its use and continued to refine the types of gases deployed, with the British using gas for the first time during the Battle of Loos in September 1915.
Among the most notorious gases used during the war was mustard gas, which made its battlefield debut in July 1917. While not as immediately lethal as chlorine, mustard gas had the sinister quality of being heavier than the surrounding air, allowing it to linger and cause harm long after its initial deployment, persisting in the soil for weeks. Its effects were savage, inflicting severe injuries upon the unlucky soldiers who came into contact with it, with the pain being described as unbearable.
Osoweic Fortress
In August 1915, Osowiec Fortress, situated in what is now northeast Poland and originally constructed by the Russian Empire a century before, became the focal point of fierce battles. Strategically positioned amid marshland, the fortress acted as a vital barrier against Germany’s expansionist goals, marking it as a prime target.
During World War I, the Germans launched multiple attacks on the fortress, enduring sustained artillery fire in response. Even the Russians recognized the structure’s resilience under such intense bombardment.
To penetrate its defenses, German forces crossed two trench lines before reaching the imposing walls and battlements, where Russian sharpshooters awaited them. This complex defensive setup enabled the Russian garrison to hold the position with only a small force.
The first major attack occurred in September 1914, when 40 infantry battalions from the German 8th Army, supported by heavy artillery, failed to take the fortress. Another barrage followed that winter, but the fortress withstood it. Despite these setbacks, the Germans were not ready to abandon their efforts quite yet…
Launching the Battle of Osoweic Fortress
Kaiser Wilhelm II was intent on knocking Russia out of the war and set his sights on seizing Osowiec Fortress to achieve this goal. In August 1915, he dedicated significant military resources to the effort, placing the operation under the command of Field Marshal Paul von Hindenburg. Hindenburg led a formidable force and was accompanied by 14 infantry battalions, a sapper battalion, 30 artillery batteries, and approximately 24 to 30 massive siege guns.
In stark contrast, the Russian garrison defending the fortress numbered only about 900 men, while German forces swelled to an estimated at 7,000 troops—stacking the odds heavily against the defenders. Still, Osowiec Fortress had earned a reputation for its toughness, and the Russian soldiers took heart in their stronghold’s track record of survival. Yet this time, they would face a terrifying new weapon—poison gas—designed specifically to break even the staunchest resistance.
Deploying chlorine gas on the battlefield
Rejecting traditional siege methods, Paul von Hindenburg oversaw a carefully coordinated chemical assault on Osowiec Fortress. German forces arranged dozens of chlorine gas cylinders to be released at once, relying on favorable morning winds to carry the toxic cloud directly into the defensive positions. At dawn on August 6, 1915, during World War I, the attack began.
The gas spread rapidly across the landscape, withering vegetation and causing severe injury to anyone caught in its path. The yellow-green cloud signaled extreme danger to those exposed. Inside the fortress, Russian troops had little in the way of protection, resorting to improvised measures such as covering their faces with damp cloths—or even urine-soaked rags—in an attempt to reduce the gas’s effects. Though these efforts provided only limited relief, they did not stop the defenders from organizing a counterattack that would soon astonish both sides.
Attack of the Dead Men
What happens when chlorine gas is inhaled? It combines with the body’s moisture to produce hydrochloric acid. Essentially, the Russians were being consumed from within by the very air they breathed. With such a deadly weapon, it seemed their fate was sealed. Many perished due to Paul von Hindenburg’s ruthless tactic, but they were far from defeated, as the Germans were about to discover.
Lt. Vladimir Kotlinsky was unwavering in his mission to drive back the enemy. He and 60 other men suffered horribly, wrapped in blood-soaked bandages and coughing up bits of their lungs as the acid ravaged their bodies. Yet, they still charged at the Germans as they breached the fortress.
It became a slaughter—but for the Germans. From the perspective of the Kaiser’s elite, they were facing what seemed like an army of the undead. The sight was so horrifying that they retreated in terror. Some were so overwhelmed with fear that they ran straight into barbed wire.
What happened to Osoweic Fortress after the Attack of the Dead Men?
Osoweic Fortress fell following the Attack of the Dead Men, but not by German hands. The Russians later took it apart themselves that month, when they realized the situation was hopeless. The soldiers that day managed to cheat death, if only briefly, to repel the enemy and maintain their might for as long as humanly possible.
While he’d led a fierce resistance against the Germans, Vladimir Karpovich perished later that evening. Prior to his death, he’d transferred control of Osoweic Fortress to the 2nd Osovetska Sap Company and Władysław Strzemiński, who himself had been severely injured in the attack.