The additional power enabled twin fixed Spandau machineguns to be fitted without any loss in performance.
Powered by the same 120 kW (160 hp) Mercedes D.III engine fitted to the D.II and based around the same fuselage, the W.IV was armed with either one (first series) or two 7.92 mm (.312 in) machine guns lMG08.
This unremarkable and derivative design was, however, transformed into a formidable fighter when it was fitted with the newly developed synchronizer gear, the Fokker Stangensteuerung, firing a single 7.92 mm (.312 in) Parabellum LMG 14 or Spandau lMG 08 machine gun through the spinning propeller.
The removal of the left-side gun is believed to have been pioneered on Oswald Boelcke's E.IV, believed to have borne IdFlieg serial 123/15, with a simpler double-synchronisation system used on the retained center-line and right side MG 08 Spandau guns.
It was armed with two 7.92 mm (0.312 in) LMG 08/15 forward-firing machine guns.
Production aircraft were armed with one or two synchronised 7.92 mm (.312 in) LMG 08/15 machine guns firing forward and a single 7.92 mm (.312) LMG 08/15 machine gun for the observer.
Initially they developed a simple adaptation of the Maxim action (itself widely used in Germany in the MG 08), driven by a crank from the engine.