Now all roads lead to France and heavy is the tread
Of the living; but the dead returning lightly dance.
Edward Thomas, Roads

Saturday, September 24, 2016

Witches' Brew: The Deadly Gas Attack at Caporetto

The single most militarily effective use of gas ever was at the northern breakthrough sector of the October 1917 Battle of Caporetto. Almost 2,000 gas canisters were fired into a flat basin on either side of the Isonzo river defended by the Italian Army's Friuli Brigade. Due to the fog that morning, sentries were slow to spot the fumes and sound the gas alarms. The new gas combination of diphenylchloroarsine and diphosgene was remarkably fast acting and efficient. Over 700 defenders quickly died at their posts and the German-Austrian forces broke through on both sides of the river, cutting off tens of thousands of Italian troops on the surrounding mountains.

Gas Launchers for the Caporetto Offensive

Diphenylchlorarsine was believed to penetrate the gas masks of the time and to cause violent sneezing and vomiting forcing removal of the protecting device. Diphosgene is a lethal asphyxiant, much more effective than the chlorine gas used earlier in the war. It irritates and inflames the inner part of the bronchial tubes and lungs and causes steady coughing, difficulty in breathing, and, frequently, acute pulmonary edema (fluid in the lungs). 

Panorama of the Northern Breakthrough Position

Below is an after-action account of a reconnaissance mission by an Austrian officer that captures both the inhumanity and the effectiveness of the gas attack near Plezzo on the Caporetto battlefield.

We had seen many terrible things, but what presented itself to our eyes on this occasion surpassed every preceding spectacle and will stay in my memory forever. There in roomy and well-supplied shelters and caverns were frozen some eight hundred men. All dead. A few, fleeing together, had fallen to the floor face down. But the majority were bunched up near the walls of the shelters, rifles between their knees, uniform and weapons intact. In a sort of barrack we found another forty bodies. Near the entrance were the officers, the non-coms, and two telegraph operators with their headsets on, a writing pad in front of them, pencils in hand. They hadn’t even tried to use their gas masks. They must have died without even being aware of what was happening. 

Italian Positions, Northern Sector Caporetto

A little later we came to a cavern, whose entrance was camouflaged with sandbags. We opened a passage and entered, shining the cone of light of our flashlight along the damp walls. At the end we saw a kind of storehouse of weapons and clothing. In a corner deeper in the room there was tangle of bodies. From the darkness there emerged some yellow streaks, faces a ghastly pallor. These for sure, had felt the blow of the gas bombs. 

Out! Away. It seemed as if we were suffocating. I grabbed Simic by the arm and we left.  

When we were further away, we removed our gas masks and dried the sweat off our brows. My colleague tried to smile to hide his dismay. We walked toward the battery without saying a word. 

Fritz Weber, Austrian Army Artillery Officer


  1. This was the attack that caused such controversy at the October 2004 beatification of the Austrian Emperor, Karl Habsburg. Italians were incensed that the Church would beatify someone who had authorized the use of such a deadly gas, especially against them!

  2. It is my understanding that diphenylchlorarsine was largely ineffective, because it was not effectively dispersed by the munitions used. It is a solid, normally, and resembled sand after a shell exploded. As described, the Italian victims do not seem to have been disabled by sneezing and vomiting, probably were not aware that they were being gassed until it was too late. Phosgene and diphosgene are practically odorless, compared with the usual stench of the battlefield. Late in the war, the British discovered that diphenylchlorarsine was extremely effective, and would penetrate German gas masks, if it was in the form of smoke. They developed an incendiary device to generate the diphenylchlorarsine smoke, but they were unable to use it before the armistice. They disposed of their stock by dropping them on Bolsheviks.