Ww1 was one big modern blood bath.
You had bolt action rifles, submarines, chemical weapons, automatic rifles, battleships, aircraft, tanks, armoured vehicles, airships, railway guns, destroyers, machine guns both heavy and light, steel helmets, armoured trains, flamethrowers and various other weapons.
What a blood bath indeed it was just showcased the horror of modern weapons but also how powerful they are.
Basically the foundation of modern warfare and changed our world forever I mean we still live with its legacy.