'There they lay... in every conceivable posture of human agony'

On Thursday, just outside the German-held village of Hulluch, a mile north of Loos, in northern France, the 16th (Irish) Division of the British army sustained one of the heaviest gas attacks of the war. Clouds of chlorine gas enveloped the Irish trenches.

A chaplain with the Royal Dublin Fusiliers wrote to his father "There they lay, scores of them (we lost 800, nearly all from gas) in the bottom of the trench, in every conceivable posture of human agony; the clothes torn off their bodies in a vain effort to breathe while from end to end of that valley of death came one long unceasing moan from the lips of brave men fighting and struggling for life."

The gas, according to one veteran, "produces a flooding of the lungs - it is an equivalent death to drowning only on dry land. The effects are these - a splitting headache and terrific thirst (to drink water is instant death), a knife edge of pain in the lungs and the coughing up of a greenish froth off the stomach and the lungs, ending finally in insensibility and death. The colour of the skin from white turns a greenish black and yellow, the colour protrudes and the eyes assume a glassy stare. It is a fiendish death to die."

Among the dead were Privates Joseph Pender and Paddy Byrne, both from Dublin. Both were aged just 17. In all, 538 men died and 1,590 were injured.

The number of deaths was significantly greater than that on all sides in the Easter Rising.