Answer:
1) Machine guns:
The machine gun allowed soldiers to rapid fire bullets at the enemy at a rate of 400 to 600 rounds per minute. This allowed defenders the ability to dominate the battlefield and cause the death of advancing enemy soldiers.
2)Tanks:
The invention of tanks made defenisve trench networks in the style of WWI obsolete. ... They were able to drive over all sorts of terrain, including trenches and they were able to smash barbed wire. They were able to move quickly, acting as cavalry used to act.
3)Poison gas:
The most widely used, mustard gas, could kill by blistering the lungs and throat if inhaled in large quantities. Its effect on masked soldiers, however, was to produce terrible blisters all over the body as it soaked into their woollen uniforms.Mustard gas, introduced by the Germans in 1917, blistered the skin, eyes, and lungs, and killed thousands. Military strategists defended the use of poison gas by saying it reduced the enemy's ability to respond and thus saved lives in offensives.
4)Flame throwers :
On July 30, 1915, flamethrowers were used effectively against British positions to flush soldiers out of their trenches and into the open. The flamethrower, like poison gas, was a psychologically terrifying weapon, leading to its use by the German Army in more than 300 battles in the war.
