On November 26, 1943 the SS John Harvey cruised into the harbor of Bari, Italy. The placid port city of 250,000, which had an old quarter dating back to the Middle Ages, had been seized by British paratroopers several months earlier without a fight. Located in southern Italy near the heel of the Italian boot, it was safely distant from the frontline to the north.

The Harvey’s cargo security officer seemed especially eager to expedite the unloading of his ship, but he could not explain to port authorities why his ship should be given priority over the dozens of others—so instead the Harvey await her turn at Pier 29 for five days. By December 2, Harvey was merely one of nine huge 14,000-ton Liberty ships in the harbor.

Indeed, the small port was swarming with more than two dozen Allied ships—one convoy lined up at the quays, unloading vast cargoes of aviation fuel and munitions, the second packed together, awaiting its turn. This vast logistical outpouring was intended to supply the British troops of the Eighth Army, then preparing for a slugging match over the fortress monastery of Monte Cassino, as well as to provide fuel and bombs for the hulking strategic bombers of the Fifteenth Air Force, which would soon begin a wide-ranging aerial bombing campaign over southeastern Europe.

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The British did not think Bari was at much risk of attack, and correspondingly did not deploy any fighters for air defense and only a small number of anti-aircraft guns. The German Luftwaffe had fought intense air battles over the Mediterranean throughout 1943, but the by the end of the year its strength seemed to be spent.

In reality, however, German feldmarschall Albert Kesselring had been convinced by Wolfram von Richthofen (cousin of the famed Red Baron from World War I), that the port was a target ripe for the plucking. On December 2, the same day that British air marshal Arthur Coningham announced at a press conference that the air war over Italy had been won, a German twin-engine Me.210 fighter photographed the harbor—the transport ships moored dangerously close to each other in an effort to expedite unloading.

By the late afternoon 105 Ju-88A4 bombers of Kampfgeschwader 54 were flying southeast into the Adriatic Sea—then swerved west to attack Bari from the east. Their approach was preceded by a few aircraft dropping strips of metallic foil to cloud Allied radars.

The harbor remained brilliantly illuminated, as port officials had kept the lights on to expedite the unloading process. This made the rows of densely packed ships the perfect target as the twin-engine bombers swooped down at 7:30 PM and unleashed their 3,000-pound bomb loads and Italian-made Motobomba circling torpedos.

One of the harbor’s refueling pipelines was severed, causing it to pour petrol into the harbor. Two ships packed full of ammunition were struck SC250 bombs, causing massive explosions. The fires reached ammunition stored inside the Harvey, causing a titanic eruption that blew the vessel apart in a cloud of flame and sent a massive concussion wave rippling across the armor that knocked ships ajar.

The flames mixed with spilled petrol and aviation fuel, causing a massive wall of fire to course across the harbor, setting additional vessels aflame. A huge cloud of oily smoke swept over the port and drifted into the nearby city, smelling rather oddly of garlic.

The German air attacks was over in less than twenty minutes, with only a single bomber shot down by flak. It left the port an inferno. No less than five huge Liberty ships had been destroyed, as well as two Canadian Fort ships of equivalent size and more than a dozen smaller transports. The ships that had escaped destruction were damaged. 34,000 tons of war materiel had been lost. You can see a footage of the aftermath here.

Hundreds of wounded, oil-slicked sailors were left floundering for their lives in the waters of the harbor. A massive rescue effort was launched to recover the mariners, while other vessels towed burning hulks out of the way of surviving ships. Two damaged British Hunt-class destroyers, HMS Bicester and Zetland, managed to wend their way through an obstacle course of burning wrecks to escape, picking up dozens of survivors as they went. British motor torpedo boats cruised around the harbor, picking up survivors from the morass. Once removed from the water, the mariners were wrapped in blankets to treat for exposure.

The fires on some of the ships raged for weeks. Meanwhile, doctors treating survivors of the attacks began to notice strange chemical burns and blistering on the survivors, many of whom complained of lesion in their eyes and swelling blisters in bodily cavities. Many had developed violent coughs as well. Some burn victims seemed to fall ill and die without apparent cause. Hundreds of civilians in Bari poured into Allied hospitals as well—even those not exposed to bomb blasts.

Rescue crews unharmed by the attack began to fall ill. The command crew of HMS Bicester became so afflicted by blindness that none were able to pilot the ship; a replacement crew had to be shuttled in to bring the vessel into port at Taranto.

Responding to suspicions of a German poison gas attack, chemical warfare expert Lt. Col. Stewart Francis Alexander flew down to Bari and examined the survivor’s injuries. He concluded that they corresponded to mustard gas, but almost no one was left alive in Bari who knew about the gas bombs. He also observed that the majority of affected mariners came from ships berthed next to Harvey. He directed an inquiry up the chain of command, which finally uncovered the astounding truth.

The Allies’ Secret Stash

Prior to the attack, Allied intelligence had received word that German chemical weapons had been moved to the Italian theater. Though all major powers in World War II maintained chemical warfare stocks, they mostly refrained from deploying them in battle for fear of the retaliatory attacks. Fearing that the German policy might change, President Roosevelt secretly authorized the movement of chemical warfare assets to Italy.

This was why the Harvey’s hold contained more than 2000 bullet-shaped M47A2 bombs pumped full of ‘Agent H’—mustard gas. A thin steel shell, less than a millimeter thick, contained the liquid sulfur mustard in the notoriously leaky bombs. Despite its low lethality rate, mustard gas was one the most dreaded chemical weapons of World War I. Mere skin contact with the carcinogenic gas would eventually cause large, agonizing blisters full of yellow pus to form on the skin and blinding conjunctivitis in the eyes. If inhaled, bleeding ulcers could form in the lungs. The gas was so corrosive, the air-dropped M47 bombs had to be coated with a special oil to protect from being eaten from the inside out.

The secrecy around the munitions meant that even the Harvey’s captain, Eliot Knowles, was not supposed to be in the know. The Harvey’s cargomaster did know about the bombs, but he wasn’t supposed to reveal that to Allied authorities in Bari.

The explosion of the Harvey had vaporized some of the gas, causing to mix with the clouds of oily smoke pouring over the harbor, which was inhaled by numerous sailors. The mustard gas had also mixed with the oil slicking through the harbor into a fatal cocktail that adhered to the skin of shipwrecked sailors. The correct treatment for such mustard-gas exposure is to remove clothing and wash off the skin. By wrapping them in blankets while wearing their poison-drenched clothing, rescued sailors had been inadvertently super-exposed. Even before he received confirmation, Steward ordered medical personal to treat victims as victims of a mustard gas attack, saving lives.

Altogether, more than 628 Allied personnel and civilians were treated for exposure to mustard gas, of whom eighty-three did not survive. However, many additional civilians fled the city after the raid and may have succumbed to the poison. Altogether, in addition to 1000 dead allied personnel, it is estimated that at least another 1000 Italian civilians perished as a result of the raid and the chemical spill.

Winston Churchill fiercely asserted that the incident needed to be covered up. Churchill believed that if the Germans got the impression that an Allied chemical attack was imminent, they might respond with a chemical attack of their own. A Nazi chemical attack would have been deadly indeed, as the Germans had invented nerve gas—an agent many times more lethal than mustard gas. Documents were destroyed, and the incident was hushed up. Still, words somehow reached Axis intelligence, as radio propagandist Axis Sally taunted Allied troops over the radio waves about the chemical spell. Nonetheless, the chemical accident wasn’t declassified until 1959, and did not become widely known until Glen Infield published Disaster at Bari in 1967.