 After the production of 20 DH.4 copies, followed by about 200 copies of the DH.9 powered by the Mercedes D.IV engine (also designated R-1) and a further 130 powered by the Siddeley Puma (designated R-2), a copy of the DH.9A powered by the M-5 engine, a Soviet copy of the DH.9A's Liberty, entered production in 1924.The Polikarpov R-4 was a modification of the R-1, with the engine lowered and moved forward by to improve both the forward visibility and the C.G position.The nose shape was improved by fairing and by installing a retractable ventral radiator.