<P> The surrender of the Russians and the Treaty of Brest - Litovsk in March 1918, and the resulting release of troops from the Eastern Front gave the Germans a "last chance" of winning the war before the Americans could become effectively involved . This resulted in the last great German offensive of the war, the "Spring Offensive", which opened on 21 March . The main attack fell on the British front on the assumption that defeat of the British army would result in the surrender of the mutiny - weakened French . </P> <P> In the air, the battle was marked by the carefully coordinated use of the Schlachtstaffeln or "battle flights", equipped with the light CL class two seaters built by the Halberstadt and Hannover firms, that had proved so effective in the German counter-attack in early October's Battle of Cambrai . The new German fighter aircraft, notably the Fokker D. VII, that might have revived German air superiority in time for this battle had not however reached the Jagdstaffeln in sufficient numbers, despite its own premier on the Western Front in the mid-Spring of 1918 . As with several offensives on both sides, thorough planning and preparation led to initial success, and in fact to deeper penetration than had been achieved by either side since 1914 . Many British airfields had to be abandoned to the advancing Germans in a new war of movement . Losses of aircraft and their crew were very heavy on both sides--especially to light anti-aircraft fire . However, by the time of the death of Manfred von Richthofen, the famed Red Baron, on 21 April, the great offensive had largely stalled . The new German fighters had still not arrived, and the British still held general air superiority . </P> <P> The month of April 1918 began with the consolidation of the separate British RFC and RNAS air services into the Royal Air Force, the first independent air arm not subordinate to its national army or navy . By the end of April the new Fokker, Pfalz and Roland fighters had finally begun to replace the obsolescent equipment of the Jagdstaffeln, but this did not proceed with as much dispatch as it might have, due to increasing shortages of supplies on the side of the Central Powers, and many of the Jastas still flew Albatros D types at the time of the armistice . The rotary engined Fokker D. VIII and Siemens - Schuckert D. IV, as well as surviving Fokker Triplanes, suffered from poor reliability and shortened engine life due to the Voltol - based oil that was used to replace scarce castor oil--captured and salvaged Allied aircraft (especially Sopwith Camels) were scrounged, not only for engines and equipment, but even for their lubricants . Nonetheless, by September casualties in the RFC had reached the highest level since "Bloody April"--and the Allies were maintaining air superiority by weight of numbers rather than technical superiority . </P> <P> 1918, especially the second half of the year, also saw the United States increasingly involved . While American volunteers had been flying in Allied squadrons since the early years of the war, not until 1918 did all - American squadrons begin active operations . Technically America had fallen well behind the European powers in aviation, and no American designed types saw action, with the exception of the Curtiss flying boats . At first, the Americans were largely supplied with second - rate and obsolete aircraft, such as the Nieuport 28, Sopwith 11⁄2 Strutter, and Dorand AR. 2 types, and inexperienced American airmen stood little chance against their seasoned opponents . As numbers grew and equipment improved with the introduction of the twin - gun SPAD XIII as well as the Sopwith Camel and even the S.E. 5a into American service near the war's end, the Americans came to hold their own in the air; although casualties were heavy, as indeed were those of the French and British, in the last desperate fighting of the war . One of the French twin - seat reconnaissance aircraft used by the French and the USAAS, the Salmson 2. A2, was among the World War I - era aircraft to pioneer the use of "fixed" radial engines in military aircraft--the liquid - cooled radials designed by Georges Canton and Pierre Unné powered the 2. A2 aircraft, and were among the first "fixed" radial aircraft powerplants ever designed, and manufactured by the parent Société des Moteurs Salmson aircraft and automobile manufacturing firm, from 1908 to 1920 . </P>

What accounted for british military superiority in the first years of the war