Glenbrook Tunnel War One. The first was Chlorine gas which was introduced by the Germans at the Second battle of Ypres in April 1915. This was followed by the use of Phosphene Gas, also introduced by the Germans. These attacked victims' respiratory organs causing coughing and choking. The Germans used Mustard Gas, a more advanced gas, for the first time at Riga (or Yperite) in September 1917. It caused both internal and external blistering in its victims. The blistering was often delayed and remained in the ground for weeks afterwards making capture of infected trenches dangerous. Protection against mustard gas was far
Action of 25 September 1917 about the new conditions produced by German defence-in-depth. The 4th Army had spread strong points and pillboxes in the areas between its defensive lines and made rapid counter-attacks with local reserves and "Eingreif" divisions ("Eingreifdivisionen", specialist counter-attack divisions), against Allied penetrations. Plumer issued a preliminary order on 1 September, which defined the Second Army area of operations as Broodseinde and the area to the south. The plan was based on the use of much more medium and heavy artillery, which had been brought to the Gheluvelt Plateau from VIII Corps, on the right flank of the Second Army and by