On the 22nd April 1915, towards the end of the afternoon, a strange yellow-green cloud appeared over no man’s land and drifts on the wind towards the French lines in the Langemarck-Pilckem sector, held by the 45th Division and the 87th French Territorial Division. Within just a few minutes, the French troops were suffocated under a cloud of chlorine gas and what few survivors remained were in full flight towards the rear. The Germans, meeting with little or no resistance, captured the Pilckem Ridge and right up to the Yser canal, opening a gaping breach between the French and Canadian lines. This volume retraces events as they unfold, as well as describing the lead-up to the battle and its immediate consequences. A large majority of the photographs which illustrate this volume have never been previously published.