What happened at Osowiec in 1915?
Osowiec was a small Russian fortress guarding the marshes of the Biebrza (Bobr) river in what is now northeastern Poland. German troops bombarded it with heavy siege guns, including 42 cm howitzers, in February and March 1915 and could not break it. On 6 August 1915 they released chlorine against its forward position. Most of the defenders there were poisoned, but companies of the 226th Zemlyansky Infantry Regiment counterattacked and retook the trenches by late morning. The Russians abandoned and blew up the fortress on 22 and 23 August 1915, as the whole front fell back. The phrase "attack of the dead men" was first used for the counterattack in 1939.7
Osowiec was one of the smallest fortresses of the Russian Empire, yet it held out longer than far bigger ones. Its siege belongs to the war told in our guide to the Eastern Front of World War I, and its gas attack grew into a legend that is still retold. This article follows the siege from beginning to end and then checks the legend against what the sources actually say.8
A fortress in the marshes
Osowiec guarded a crossing of the Biebrza, the river that Russian sources call the Bobr, in what is now northeastern Poland. Its valley was a wide marsh, flooded in spring and autumn, with no other crossing on that stretch, and the railway and road from East Prussia to the rail junction of Białystok ran straight through it.9
The Russians began building the fortress in the 1880s, starting with a barrier fort beside the railway that grew into the Central Fort, or Fort 1. Further forts followed on both banks of the river. Sergei Khmelkov, a military engineer who served in the fortress, adds that new concrete barracks and shelters built from 1912 were what let the garrison ride out the heaviest bombardment.10
Russian documents of the time used the Julian calendar, 13 days behind the Western one, so the same day appears under two dates. The 1917 study of the siege, written by two of its senior officers, puts the gas attack on 24 July, which is 6 August in the Western calendar. This article gives Western dates.11
1914 and the winter of 1915
The Germans first attacked Osowiec in September 1914. Khmelkov describes it as a short affair at the end of the month, five or six days of fire from 15 to 20 cm guns, after which the Germans withdrew to East Prussia.12
The real siege began in the winter. In February 1915 German armies attacked the Russian Tenth Army in East Prussia and drove it back, and the 57th Infantry Division fell back on Osowiec to join its garrison. Among its units was the 226th Zemlyansky Infantry Regiment.13
For about two weeks the retreating troops fought on the forward positions north of the fortress, around Ciemnoszyje and Białaszewo. On the night of 21 to 22 February they pulled back to the Sosnya position, the forward position just in front of the fortress, and the siege proper began.14
In front of the fortress stood a German blockade corps built around the 11th Landwehr Division, about 40 battalions in all by both Russian accounts. The 1917 study counts 26 Russian battalions on a front of about 60 versts, only 11 of them first-line troops and 8 of them militia.15
Big Berthas against a small fortress
The Germans brought up the heaviest guns they had. Both Russian accounts count 66 to 68 heavy siege guns, among them 30.5 cm mortars and two or four 42 cm howitzers. The biggest batteries stood 8 to 12 kilometers from the forts, out of range of the fortress artillery.16
The bombardment began in the last days of February (on 25 February by Khmelkov's account) and was heaviest at the end of the month, when the 42 cm guns joined in. The estimates of what was fired differ widely: the 1917 study gives about 120,000 shells, Khmelkov writes of about 200,000 "by some data" but notes that only about 30,000 craters were recorded. Many shells, he suggests, vanished into the river, the marshes and the water-filled ditches.17
The damage was real but not decisive. Wooden and brick buildings were wrecked and the roads so cratered that bridges had to be laid over the holes, but the concrete casemates cracked without collapsing. Russian and French newspaper correspondents compared the fortress to hell. Khmelkov writes that the infantry regiments suffered almost no losses and that the commandant, Major General Brzhozovsky, reported there was no reason to fear for the fortress.18
According to Khmelkov, on 28 February two long-range 15 cm Canet guns, just arrived from Kronstadt, knocked out two of the 42 cm howitzers at a railway halt behind the German lines. The 1917 study is more careful and says only that there was evidence that two 42 cm howitzers were among the German guns damaged. Either way, in March the fire slackened. The 1917 study puts this down to the Germans losing confidence that they could take the fortress by storm.19
Spring and summer: siege by sap
Spring helped the defense. The river overflowed, the marshes filled with water, and the approaches became impassable. The 1917 study writes that this let the command reduce the garrison by about half, to 15 battalions by the end of March.20
Through the spring and summer the Germans dug saps toward the Sosnya position. By late July, Khmelkov writes, their trenches were 150 to 200 meters from its wire, and they were doing earthworks in front of them that the garrison did not understand. Only later did it learn that they had been installing gas cylinders.21
6 August 1915: the gas
Chlorine was a new weapon. The first large-scale gas attack of the war had come at Ypres on 22 April 1915, as told in our article on the battles of Ypres, and the garrison of Osowiec had nothing effective against it.22
The Germans set up 30 or more gas batteries with several thousand cylinders in front of their trenches and waited for a wind blowing toward the fortress: more than ten days by Khmelkov's account, about 13 days according to prisoners quoted in the 1917 study. About 12 to 14 battalions of the 11th Landwehr Division stood ready to follow the cloud.23
On the Russian side the Sosnya position was held by only nine companies, five of the Zemlyansky Regiment and the rest militia. The extra battalion sent forward every night had gone back to the Zarzeczny fort to rest at about 3 a.m.24
At 4 a.m. on 6 August the Germans opened the cylinders. A dark green cloud reached the Russian trenches in 5 to 10 minutes. The 1917 study identifies chlorine with some other admixture, Khmelkov chlorine with bromine. Its effects were felt about 12 kilometers away. The anti-gas bandages of the time gave little protection. By the 1917 study's account almost all the defenders of three of the four sectors of the position, and half of the fourth, were mortally poisoned, and the regimental diary also records the mass poisoning of those sectors.25
Behind the gas and a heavy barrage, the 18th Landwehr Regiment cut gaps in the wire on both sides of the railway, took the first and second sectors and pushed toward the reserve trenches. The 76th Landwehr Regiment, attacking Sosnya village, walked into its own gas. The 1917 study claims it lost about a thousand men dead, Khmelkov speaks only of enormous losses.26
The day is also told in our 6 August page of military history.
The counterattack
With the Germans approaching the reserve and nothing behind it but the Zarzeczny position, the fortress artillery laid a barrage in front of the position and the 8th, 13th and 14th Companies of the Zemlyansky Regiment were sent forward from the Zarzeczny fort to counterattack.27
The 13th Company was led by Second Lieutenant Vladimir Kotlinsky. It had already lost men to the gas (20 men by the 1917 study's count, up to half by Khmelkov's), and Kotlinsky himself was poisoned. It advanced along the railway and charged the German lines from 400 to 500 paces. Kotlinsky was mortally wounded and handed the company to a sapper officer, Second Lieutenant Strzheminsky. By the 1917 study's account Strzheminsky then led the bayonet charge that drove the Germans out of the first and second sectors. The regimental diary has Kotlinsky fall only at the end of that charge, with Strzheminsky completing it.28
The fortress artillery, nine heavy and two light batteries, then concentrated its fire on the last German strongpoint, the Leonovo farm, and it was retaken. Men of the 12th and 14th Companies cleared Sosnya village. By about 11 a.m. the whole position was back in Russian hands, by the regimental diary as early as 8 a.m. The Russian accounts count 30 to 40 prisoners, and the Germans did not attack again.29
The losses are uncertain. The regiment's war diary, quoted by Alexander Cherkasov and his co-authors, lists one officer killed, seven officers dead from gas and 20 officers and two doctors gassed. It gives no figure for the rank and file, whose dead the authors estimate at about 200. The historian Gennady Mokshin gives 200 to 600 dead by various accounts and up to 900 more casualties. The curator of a 2015 exhibition at the Muzeum Wojska in Białystok spoke of over 1,500 dead.30
Evacuation, August 1915
The gas attack was the last assault. By August the Russian armies were retreating from Poland, and the fortress was ordered to prepare its evacuation, the removal of its guns and stores, and its demolition.31
Guns and stores were moved out first, and the garrison was formed into a corps under the commandant. The sappers blew up the forts, barracks and batteries. The 1917 study dates the demolitions and the departure of the last troops to the night of 22 August, Khmelkov puts the explosions on the evening of 23 August.32
German troops entered the ruins two days after the Russians had gone, on 25 August by Khmelkov's account. That is why the fortress is often called unbeaten. Khmelkov contrasts it with Novogeorgievsk, Kovno and Grodno, which did not fulfill their purpose, and above all with the huge fortress of Novogeorgievsk, which surrendered after 10 days while Osowiec held out for 190.33
The attack of the dead men: legend and sources
The earliest detailed account, the 1917 study, praises "the famous gas assault, so brilliantly and selflessly beaten off by units of the glorious Zemlyansky Regiment" (our translation). It uses the word "dead men" only once, for 36 dead Russians whose skulls, it says, the Germans smashed in Sosnya. Mokshin finds nothing sensational in the earliest accounts.34
The legend starts with Khmelkov's book of 1939. He wrote that the counterattack of the 13th Company, "this attack of the dead men", as an eyewitness put it, so struck the Germans that they fled, and that a few dozen poisoned men put three Landwehr regiments to flight. Mokshin points out that, read in context, the attack was beaten off by all the survivors fit to fight, not fewer than 200 men counting the gunners.35
Later retellings added more. Mokshin traces the modern revival to a newspaper article of 2009, in which just over 60 men, wrapped in rags and coughing up pieces of their lungs, put 7,000 Germans to flight without a fight, and versions like it spread across the internet. The Polish historian Bogusław Perzyk, as summarized by Mokshin, found that the counterattack began about two hours after the cloud had passed, that only a few men were poisoned by gas left in the trenches, and that the roughly 150 men of the 13th Company faced two German assault groups of about 80 men in all.36
The regimental diary studied by Cherkasov and his co-authors confirms the charge, Kotlinsky's death and the recapture of the trenches, but not the shout of "hurrah" that the 1917 study and Khmelkov describe. The authors think the gassed men probably did look as grim as the popular accounts say, and they conclude that the "attack of the dead men" was a successful counterattack.37
Other stories have grown around the fortress too. The 1917 study records a German soldier caught as a spy who claimed he had been sent to offer the commandant 500,000 marks to surrender. Mokshin traces the later version, in which German envoys made the offer to Svechnikov, to a novel by Valentin Pikul. He also notes that the phrase "Russians do not surrender", often linked to Osowiec, is missing from reference books of quotations, and that the claim it went around the world during World War I has not been confirmed.38
