On 22. April 1915, a wall of greenish-yellow fog, up to 2m high, was slowly creeping towards the Allied lines on the Ypres salient. A sweetish-chloric smell preceded the horrific effects of the deadly gas. Coughing, spitting, and retching, men were abandoning their trenches, hurrying to the rear, or falling to the ground, clutching their throats. It was the same desperate, gruesome scenery, the Russian soldiers at Osowiec Fortress had to fight through. From then on, a scientific race to counter and protect against those deadly chemicals began.