The technological advancements made during World War I made it extremely different than wars before.
For example, the creation of the machine gun allowed for hundreds of rounds of ammunition to be shot at enemy soldiers in mere seconds. This greatly increased the amount of casualties and also affected how soldiers fought in World War I. Dangerous guns like this made them reconsider running into battle.
Another example is submarines. Unrestricted submarine warfare left navy forces paralyzed, as their was little warning of an incoming attack.