The SPAD (Societe pour l'Aviation et ses Derives - Society for Aviation and its Derivatives) XIII was designed in 1916 as a French attempt to counter the twin gun German fighters, like the Halberstadt. The SPAD XIII doubled the firepower of the earlier SPAD VII by using two Vickers 303 machine guns with 400 rounds of ammunition for each gun. The enthusiasm of the French pilots who tested the aircraft between April and September 1917 encouraged the French government to order more than 2,000. The U.S. Air Service also began flying the SPAD XIII in March 1918 and by war's end in November 1918 the Air Service has acquired 893. Throughout 1917 and into 1918 the SPAD XIII held its own against German aircraft, but in the summer of 1918 it was outclassed by the newly arrived Fokker D.VII. The SPAD XIII had poor visibility and insufficient rate of climb, but it proved itself a rugged fighter with the ability to dive at high speed to escape enemy planes.