Transportation technology was very different in World War I than in any other war. The main mode of transportation was the railway. Railways dominated in World War I. Through railways, men could be moved quickly to the battle front, but the railways were vulnerable at the front itself
One of the first poisonous gases used during the war was chlorine gas. It appeared to be a simple smoke screen, but it was deadly when breathed in causing many casualties
Later, other poisonous gases were used such as mustard and phosgene which were also very deadly