mm (.312 in) calibre lMG 08 "Spandau" machine guns, while most E.IIIs and the production E.I through E.III Eindecker models used only one of the same model. The final variant was the Fokker E.IV which received a 119 kW (160 hp) Oberursel U.III, 14 cylinder twin-row rotary engine (a copy of the Gnome Double Lambda rotary) and was fitted with twin machine guns as standard, after repeated failure of an experimental triple-gun installation, which was initially intended be standard for the E.IV. Total production for the entire Fokker E.I through E.IV series was 416 aircraft (the exact breakdown by type is not clear, although the E.III was the most important model). Operational history The first Eindecker victory, though unconfirmed, was achieved by Leutnant Wintgens in the late afternoon of 1 July 1915 when, while flying one of the five M.5K/MG production prototype/"service test" aircraft, numbered 'E.5/15' near Lunéville, he forced down a French Morane-Saulnier L two seat "parasol" monoplane. By this time the first E.Is were arriving as supplementary equipment, one per unit as "attached" aircraft, for the ordinary Feldflieger Abteilung - initially to provide escort protection for their usual quantity of six two-seat reconnaissance biplanes per unit. Three days after his "unconfirmed" victory, Wintgens downed another "Morane Parasol" with the same E.5/15 aircraft, and a full fortnight after his initial engagement, on 15 July 1915, he became the first Eindecker pilot to be credited with such an official victory. The two most famous Eindecker pilots were Oswald Boelcke (initially flying M.5K/MG service test aircraft E.3/15) and Max Immelmann, both of Feldflieger Abteilung 62 - who himself received his first production E.I Eindecker for his own use, bearing IdFlieg serial number E.13/15 just before July 1915's end; and who each scored their first kills in E.Is in August 1915, just after Boelcke became the sole pilot flying the E.3/15 service test aircraft. Leutnant Otto Parschau, who was instrumental in the introduction of the Eindecker from the very start, flew the M.5K/MG aircraft numbered E.1/15, after the Fokker factory took back his now worn-out A.16/15 aircraft a second time, this time to be retained by the Fokker factory for development purposes. Immelmann's initial E.13/15 Eindecker survived past the end of the war. Oswald Boelcke scored the most Eindecker victories - 19 out of his final tally of 40. His last victory in an Eindecker occurred on 27 June 1916. Max Immelmann