What if machine gun were never invented ? The cumbersome Gatling gun become main armaments instead of machine gun, positioned in wheels carriage like a cannon and were used in very limited number. Luxurious machine. Most of the army in 1900 doesn't have any piece of it except USA, British (limited), Germany, A-H (Supplied by Germany), Russia (one or two in every division)... Hence cavalry still a mainstay in a Great War.