I answered similar questions a while back^
Suffice to say, the armies of 1918 would have been unrecognizable from the armies of 1914. Predicted, massed artillery fire, with pieces of all sizes and calibre; advanced, small-unit tactics, combining fire and movement with platoon level weapons systems like mortars, grenade launchers and light machine guns; motorized transport, and the beginning of mechanization in the form of tanks, armoured cars, tractors, even early self-propelled guns and APCs; coordination of ground forces and air forces, along with the widespread use of aircraft for reconnaissance, artillery observation, ground attack and bombing; above all, the enshrining of combined arms warfare in the conduct of modern war, with infantry, artillery, tanks, aircraft, cavalry, etc coordinating their efforts on the battlefield.
Essentially, by 1918 you would have been looking at the shape of things to come. By the 1930s there would be wireless radios, massed tank forces, motorized/motorising armies, and fleets of aircraft for bombing, air defence, and ground support.