Final answer:
In response to a chemical gas attack, soldiers had to quickly don gas masks, and witnessing such an attack would typically leave the observer shocked due to the devastating and terrifying nature of chemical warfare during World War I.
Step-by-step explanation:
The soldiers have to hurry to quickly put on gas masks. After seeing the gassing, the speaker is shocked.
During the harrowing experiences of World War I, gas attacks were among the most feared encounters on the battlefield. Throughout the war, the development and use of chemical warfare necessitated the rapid donning of gas masks by soldiers, which needed to be done quickly to prevent the horrific effects of the gas. The psychological impact on those who witnessed or survived these attacks was enormous, often leaving them shocked by the devastation.