the ship indistinct, which in turn prevented submarines from determining the heading or speed of the ships. This innovation was short-lived, however, as the stark lines intended to confuse submarines only made ships into more visible targets for aircraft. The final evolution of camouflage was into the now prevalent gray shades which almost all warships since WWII have been painted. In the US Navy this is known as "Haze Gray." Development of the submarine Tactically, submarines of the First World War were similar to privateers in the age of sail, because they were employed primarily to destroy the enemy's merchant traffic in an extremely opportunistic sense rather than engage in battle with enemy naval vessels. Individually, submarines were only capable of sinking a small number of ships because of their limited supply of torpedoes and shells. Anti-submarine tactics were in their infancy at the outbreak of the First World War. Surface warships lacked the means to detect submerged submarines or the weapons to attack them. Surface warships were reduced to hoping to sight the periscope of a submerged submarine or the wake of its torpedoes. Other than gunfire, the only way to sink a submarine was by ramming. Defensive anti-submarine tactics largely consisted of turning ships end-on to the submarine, to reduce the size of the target, by turning towards a submarine sighted off the bows and away from a submarine sighted off the stern. By the end of 1914, German cruisers had largely been cleared from the oceans and the main threat to shipping came from U-boats. The British Admiralty was slow to respond to the change. Only in 1917, at the urging of the British Prime Minister, David Lloyd George, did the British institute a convoy system. Losses to U-boats dropped to a fraction of their former level. Development of aircraft During WWI, the German forces occasionally employed Zeppelins to attack enemy shipping, but this never inflicted serious losses. Towards the end of the war, the British began to develop the first aircraft carriers by adding flying off and then landing decks to the large light cruiser Furious. The interwar years Fearing another naval arms race, the big naval powers agreed to the Washington Naval Treaty and scrapped some of their battleships and cruisers while still on the slipways. In addition to this, the Washington Naval Treaty established limits on the total tonnage of the fleets of America,