Poisonous gas was used in World War I to kill many people. It was very dangerous for soldiers and people in war. Soldiers were required to bring and where gas masks to protect against the gas.
Machine guns contributed to a huge increase in death involved in war. Machine guns allowed people to shoot and kill more people.
Tanks were made in response to trench war fair. They were used to mobility to soldiers in trench war fair. Derived from tractors, tank had a top speed of 4 mph, and had the ability to cross a variety of terrain.
At the start of a World War One, German had 29 U-Boat which sank 5 British Cruisers, this resulted in a lose of 1.4 million ton of Allie shipping. The Submarine helped develope under water warfare.