What new weapons and technology were developed during world war i and how did they affect combat?

The tank was made. It made a revolutionary effect. It was based on the creation of the grenade that didn't happen to long before that. Tanks were a big armored vehicle that you can drive and blow things up with and has a hatch on top and a little thing in the front where you can see very little which was one of the negative consequences.

Democracy and darwinism would be my answer.