Chemical weapons and the United Kingdom army against British and Canadian soldiers near Ypres, Belgium, in 1917 and later also against the French Second Army. The name Yprite comes from its usage by the German army near the town of Ypres. The Allies did not use mustard gas until November 1917 at Cambrai, France, after the armies had captured a stockpile of German mustard-gas shells. It took the British more than a year to develop their own mustard gas weapon, with production of the chemicals centred on Avonmouth Docks. (The only option available to the British was the Despretz–Niemann–Guthrie process). This was used first in September
Battle of Arras (1917) the Western Front, in Operation Alberich. By the spring of 1917, the German army in the west had a strategic reserve of "Experience of the German 1st Army in the Somme Battles", ("Erfahrungen der I Armee in der Sommeschlacht") was published on 30 January 1917 by Ludendorff but new defensive methods were controversial. During the Battle of the Somme in 1916 Colonel Fritz von Loßberg (Chief of Staff of the 1st Army) had been able to establish a line of "relief" divisions (), with the reinforcements from Verdun, which began to arrive in greater numbers in September. In his analysis