How has war changed between 1918 and 1945?

Between 1918 and 1945, war-making changed in several decisive ways. The use of air forces and armored vehicles on unheard-of scales, and with previously unimaginable efficiency, was one decisive change. Another was the invention and successful deployment (or, use) of atomic weapons, which ushered in an entirely new age of both war and geo-political dynamics.