Shortly before dawn on August 6, 1915, the Russian defenders of Osowiec Fortress braced for another German bombardment. They had survived two sieges already, holding a vital rail junction on the eastern front despite being outnumbered ten to one by the attacking Germans. Some nine hundred Russians, a mix of soldiers and militia, manned the fort. Field Marshal Paul von Hindenburg had insisted the fortress be taken by any means necessary, and on that morning the Germans unleashed what they hoped would end the siege for good.

At four in the morning, artillery fire began to fall. The Russians prepared for the familiar routine. But soon a strange green fog drifted through the trenches and into the fort. It burned their eyes and sent them into violent coughing fits.

With every breath, their lungs filled with blood. Chlorine gas, which became hydrochloric acid on contact with soft tissue, dissolved the defenders from within. The men had no gas masks. Those farthest from the front soaked rags in water or urine and pressed them to their faces in desperation, but it was pointless.

Within minutes, all nine hundred defenders lay collapsed, blood pouring from their eyes, noses, and mouths. About an hour later, German soldiers wearing gas masks advanced into the fortress. They found a scene of extraordinary horror. Bodies lay contorted in agony, their makeshift masks stained red, their blinded eyes raw and gaping.

The Germans had never witnessed this kind of warfare before, and what they saw shook them deeply. But as they moved deeper into the fort, they heard something impossible. Rustling came from among the bodies. Then groans and gurgling coughs.

One by one, the fallen Russians began to rise. The last surviving defenders, perhaps sixty men, had been spared the worst of the gas by their position in the rear. They dragged themselves upright, blood streaming from their faces, choking up fragments of lung, and stumbled forward with their bayonets. The Germans, already horrified by the battlefield and now seeing what they believed were the dead returning to life, bolted in panic.

The Russians, many of them dying as they walked, opened fire on the retreating enemy. German soldiers impaled themselves on their own barbed wire trying to escape, and hundreds more were trampled under the feet of their own desperate comrades. The German army withdrew. The siege ended, and the fortress remained in Russian hands.

The Russians who had risen from the gas attack did not survive long. They fought long enough to see the Germans flee, and then they died. The fortress itself was abandoned by the Russians during a strategic retreat a few weeks later and dismantled rather than surrendered. Yet the legend of the Attack of the Dead Men, as it became known, preserved the memory of that day when a handful of dying soldiers drove a German army from the field.

Miles to the west and nearly four centuries earlier, another fortress faced an even greater enemy. In the summer of 1566, the Ottoman Empire under Suleiman the Magnificent was at the height of its power. After four decades of conquest, the aging sultan was determined to take Vienna, the last great obstacle on the road into Europe. He was in his seventies, his health failing, and he knew the time for invasion had to be now.

On April 29, he led his army west. On the way, his forces stopped at a small fortress named Szigetvár, defended by a man Suleiman knew well: Croatian Count Nikola Zrinski. The two men had faced each other before. Zrinski had helped defend Vienna in 1529 and had repeatedly frustrated Suleiman’s campaigns.

Now the sultan wanted to destroy him once and for all. The fortress was large enough to slow the march, but it was no capital. Suleiman expected to crush it quickly. He deployed his full army around Szigetvár and began the siege.

Zrinski had only 2,300 Croatian and Hungarian defenders. The Ottoman force surrounding him numbered one hundred thousand with three hundred cannons. The fortress itself was built on three islands, each with its own fort, connected by bridges. To take it, the Ottomans would have to break through three separate defenses.

Zrinski planned to make each step as costly as possible. The Ottomans opened their assault on August 6. Their cannons quickly shattered the new town, but the defenders repelled the first infantry assault and inflicted heavy losses. On August 9, with the walls collapsing, Zrinski ordered his men back across the bridge to the old town.

Suleiman arrived in person that same day, determined to witness Zrinski’s end. The Ottoman attack on the old town began on August 10. The defenders threw back ten full-scale assaults, but on August 19 the old town fell. Zrinski’s survivors fell back into the citadel.

A handful of men, caught near the leading edge of the retreat, were cut off and forced to watch as the gates closed behind them. Only six hundred defenders remained. Suleiman, suffering from illness and running low on patience, sent messages to Zrinski. He offered him rule over all of Croatia if he would abandon the Habsburgs.

There was no reply. Letters were fired into the citadel promising mercy for any man who surrendered. No one came out. A final attack breached the citadel walls and set the buildings on fire.

But the assault stopped as suddenly as it had begun. A wave of dysentery had swept through the Ottoman camp, and Suleiman himself lay dying in his tent. He died on September 6. His commanders kept the death secret, terrified that the army, already bloodied beyond expectation, would dissolve if the truth came out.

The next day, the Ottomans attacked one last time. Greek fire engulfed the battered citadel. Zrinski armed his remaining men, rolled a mortar up to the gate, and swung the doors open. The cannon fired into the packed Ottoman ranks on the bridge.

Then he led his six hundred men in a final charge. Zrinski fell almost immediately, struck by two bullets. His men surged around him and threw themselves at the enemy. The charge lasted only moments, and the surviving defenders were overwhelmed.

The Ottomans rushed through the open gates to finish the fight, but they found only a single wounded soldier seated inside, holding a torch. He ignited the remaining gunpowder supply, and the explosion killed three thousand more Ottoman soldiers. The campaign had been intended as a brief detour. It cost the Ottomans more than twenty thousand men and their sultan.

Suleiman’s successors never reached Vienna, and the siege of Szigetvár marked the beginning of the empire’s long decline. The fortress fell, but the man who defended it had accomplished what he intended. On the other side of the world, in the autumn of 1897, the British Indian Army was fighting tribal forces in the Northwest Frontier of India. Forts Gulistan and Lockhart, manned by Sikh soldiers of the 36th Sikhs, had withstood repeated attacks.

The Afghan tribesmen, frustrated by their failures, looked for a weaker target. They found one in the tiny village of Saragarhi, where a signaling station relayed Morse code messages between the two forts. If the station fell, the forts could not coordinate a defense. Only twenty-one men were stationed there.

On the morning of September 12, the soldier manning the tower spotted a large force of tribesmen approaching. He signaled Fort Lockhart for reinforcements. The reply was immediate and bleak: no reinforcements could be sent. The other forts could not spare men, and all available units were too far away.

The fort estimated the approaching force at ten thousand. The commander, Havildar Ishar Singh, told his twenty men that they would fight to the end. They could not win, but they could hold long enough to buy the other forts time. The men barricaded the gates, took positions along the walls, and waited.

The tribesmen attacked at nine in the morning. The Sikhs were superb marksmen, and the first wave fell back with heavy casualties. A second assault pushed closer, and the defenders began to take losses. For a force of twenty-one men, every death was crippling.

The tribesmen, exhausted by their losses, offered the defenders gold and safety in exchange for surrender. The answer came as gunfire. Frustrated, the tribesmen set fire to the brush around the fort, filling the air with thick black smoke. Under that cover, they moved around the fort toward the unguarded signaling tower.

The wall gave way, and screaming tribesmen poured through the breach. Ishar Singh sent men to shore up that gap, leaving the front gates vulnerable. Soon the enemy broke through there as well. With ammunition running low, the Sikhs fought with bayonets and swords.

The men at Fort Lockhart watched through field glasses as the fight descended into brutal hand-to-hand combat. Singh ordered the survivors to retreat into the inner walls and then stood alone against the oncoming mob. His stand bought his men enough time to close the inner gates. Then he was cut down.

The final defenders were overtaken within moments, their ammunition exhausted. Only the signalman remained in the tower. His last message to Fort Lockhart was simple: extended permission to take up my rifle. The commander at Lockhart gave his consent.

The soldier stowed his signaling gear, fixed his bayonet, and killed forty more tribesmen before the attackers set the tower on fire and burned him alive. The stand at Saragarhi lasted six hours. The twenty-one defenders were all killed, but they had delayed the tribesmen long enough for reinforcements to reach the two forts the following day. When they arrived, the forts were secure, and any new attack was easily repulsed.

British forces recovered the ruins of the signaling post and found the bodies of the twenty-one Sikhs surrounded by more than six hundred dead tribesmen. Havildar Ishar Singh and his men were posthumously awarded the Indian Order of Merit, the highest gallantry award an Indian soldier could receive at the time, equivalent to the Victoria Cross.