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
Actions of 30 September – 4 October 1917 the counter-attack. After the attack of 26 September, the British had used information from prisoners, gleanings from the battlefield and ground observation to judge the state of the 4th Army. The concentration of the German heavy artillery into the Tenbrielen, Kruiseecke, Becelaere and Keiberg groups directed towards Menin Road Ridge, Tower Hamlets Ridge, Polygon Wood and Broodseinde Ridge was reported on 29 September by I Anzac Corps flash spotters; RFC reconnaissance flights confirmed the changes but this took from 1 to 2 October, because Germans hid the redeployment with smoke screens. By 29 September, the 4th Army had recovered from