In the first years of the war there were still vestiges of 19th century warfare. For example, cavalry were still used. But the killing power of the machine gun soon rendered such heroics pointless. Artillery too had changed out of all recognition from the pieces that had been used in the last major European conflict, the Franco-Prussian War, which had ended barely 30 years earlier. The infantryman now carried a rifle instead of a musket. The first terror weapon to make its presence felt on the battlefield was gas. But the most enduring weapon to appear during WW1 was the tank. A British invention, it first appeared on the Somme in 1916, and although it made little contribution in those terrible first days, it terrified the Germans, and would prove to be a decisive weapon during the following year, when Germans resistance nearly completely disintegrated during the Battle of Cambrai.
Arguably the most significant development of the First World War was the advent of Air Power. In 1909, Europe was amazed when Louis Blériot just managed to fly across the English Channel. By 1918, aircraft could carry several thousand-pound bombs over 1000 miles to attack cities. The Aeroplane completely changed the whole face of conflict on land and at sea. By the end of the war, all the fundamental roles of Air Power had been tried: Reconnaissance, Communications, Air Superiority, Transport, Strike and Heavy Bomber.
WW1 saw the beginning of the end of Britain's dominance at sea. By far the most significant development was the submarine. The German U-Boats were able to challenge Britain's blockade of European waters, as well as take the conflict, usually undetected until it was too late, right to the American shoreline. Another weapon to make its debut in the latter years of the war was the aircraft carrier. Although converted from battleships and freighters, the first carriers played a vital part in shaping the vessels (and wars) of the future.