Answer:
It changed the way people thought about war.
Step-by-step explanation:
During WW1 trench warfare was almost use exclusively, it is an extremly slow form of war. It breaks soldiers done with what they called shell shock (more commonly known as ptsd) because they would just continuesly hear explosions.
Once WW2 started the Germans used lightning ware fare, which is when they strike really fast and precisely. It worked very well, strongly because ww made everyone think that with modern technologies that the only way to fight a war is with trench warfare.