1. Modern Warfare

2. Trench Warfare
It was invented in 1914 by British troops. Its purpose was so defending units could be protected by small fire and sheltered against artillery. It was used in most battles during the war. It was commonly used in Eastern and Western front. Casualty rate estimates vary from 8.5 to 12 million.

3. Chemical Warfare
It was invented on April 22, 1915 by Fritz Haber. Chemicals were used incapacitate enemies, not to kill them. Basically everyone use chemicals during the war.

4. Total Warfare
Total warfare is basically being able to attack anyone and use any weapons. They could attack anyone, including normal citizens, if they were near where they were hiding.

5. Tanks
It was invented on September 6, 1915 by Lieutenant Colonel Ernest Swinton in England. They were used by Great Britain, France, and Germany.

6. Airplane
It was invented on December 17, 1903 by the Wright Brothers. It was used to bomb other countries. It was used by most countries in the war. British lost 245 planes during WW1.

7. Machine Gun
It was invented in 1884 by Helge Palm Crantz. It was used for rapidly advancing infantry troops. It was used in all battles. 20% of casualties were caused by the machine gun.

8. Zeppelin
It was invented in 1900 by Ferdinand von Zeppelin. It was used to bomb more strategically. It was used in the attack on London.

9. Barbed Wire
It was invented in 1867 by Lucien B. Smith. It was steel fencing used to construct inexpensive fences. It was used in in many different battles to defend trenches. It was used from the coast of France all the way to Switzerland.

10. Submarine
It was invented in 1620 by Cornelius Jacobzoon Drebbel. It was used to sink other boats and defend. It was used in the first battle of the Atlantic. Germany used it. There were more than 5000 ships sunk.