USA HISTORY

Detailed explanation-1: -Able to crush barbed wire and cross trenches, tanks moved forward through machine gun fire and often terrified German soldiers with their unstoppable approach. Chemical warfare first appeared when the Germans used poison gas during a surprise attack in Flanders, Belgium, in 1915.

Detailed explanation-2: -World War I popularized the use of the machine gun-capable of bringing down row after row of soldiers from a distance on the battlefield. This weapon, along with barbed wire and mines, made movement across open land both difficult and dangerous. Thus trench warfare was born.