figures running wildly in confusion over the fields. 2 A British soldier described the pandemonium that flowed from the front lines to the rear. Within a matter of minutes, this slow moving wall of gas killed more than 1000 French and Algerian soldiers, while wounding approximately 4000 more. The surprise use of chlorine gas allowed the Germans to rupture the French line along a 6-kilometer (3.7-mile) front, causing terror and forcing a panicked and chaotic retreat. Disregarding intelligence reports about the strange cylinders prior to the attack, the French troops were totally unprepared for this new and horrifying weapon. The order to release the gas was entrusted to German military meteorologists, who had carefully studied the area’s prevailing wind patterns. Filled with pressurized liquid chlorine, the cylinders had been clandestinely installed by the Germans more than 3 weeks earlier. Within 10 minutes, 160 tons of chlorine gas drifted over the opposing French trenches, engulfing all those downwind. After a while, condensation in the mask built up, which severely encumbered the wearer, requiring the mask to be taken off.IN THE LATE AFTERNOON OF April 22, 1915, members of a special unit of the German Army opened the valves on more than 6000 steel cylinders arrayed in trenches along their defensive perimeter at Ypres, Belgium. The M2 protected the wearer for at least five hours against the common World War I chemical weapon phosgene. These two glasses were held in place by a metal ring on each eyehole, with 12 dents in each so as to better hold the glass on the mask. In April, the rectangle was replaced by two round pieces of cellophane glass due to problems on the earlier model, which could not be cleaned without removing the glass. The first model of the M2 mask was introduced during March 1916 and had a rectangular piece of cellophane glass for viewing, protected by a piece of glass in front of it. During 1917, an additional mask strap was produced, intended to be worn around the head of the wearer. Instead, it was made of one piece of material which covered the face completely. In contrast with gas masks made later in the war, the M2 did not have a special filter that fit onto the mask. While switching gear, some soldiers inhaled the poison gas and became casualties. The untrained soldiers tended to put on the Small Box Respirator when first confronted with a gas attack and then switch to the M2 when they realized they would have to wear it for a long time. The US Army issued its soldiers the British-made Small Box Respirator to protect against chemical attack, and the French-made M2 gas mask in case a mask had to be worn for an extended period of time. When the United States entered World War I in 1917, it was unprepared for chemical warfare. British forces were issued 6.2 million units of the second model between May and November 1916 and used it as late as August 1918.

A second model introduced in April 1916 was produced in three different sizes and included two separate eyepieces, so folding it would not cause damage. The first M2 model was produced in only one size and often incurred damage when it was folded for placement in a metal container. An order of 600,000 masks was produced in February 1916 and introduced for British forces the following month. The M2 mask was based on a design proposed in 1915 by René Louis Gravereaux of Paris. It was intended to protect the wearer from at least five hours' exposure to phosgene gas, a common chemical weapon of the time. The M2 was fabricated in large quantities, with about 29,300,000 being made during the war. The M2 gas mask was a French-made gas mask used by French, British and American forces from April 1916 to August 1918 during World War I. French-made gas mask American soldiers wearing M2 gas masks in a frontline trench (1919 postcard image)

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