SB 2M-100 "Katiushka" Spanish Air Force Bomber

SB 2M-100 – first production model. Wing area increased to 56.7 m2 (610 ft2). Equipped with Klimov M-100 engines (the Hispano-Suiza 12Y built under licence) driving two-bladed propellers

While only 54 SBs had been delivered to the Soviet Air Forces by 1 July 1936, this did not stop the new Tupolev bomber being amongst the first shipments of military equipment sent by the Soviet Union to support the Spanish Republicans when the Spanish Civil War broke out on 17 July 1936. An initial batch of 31 SBs arrived in Cartagena aboard the Soviet Freighter Komsomol in October 1936, flying their first mission, a bombing raid by four SBs against Tablada airfield, Seville on 28 October. The SBs were used to equip Grupo 12 of the Spanish Republic Air Force, which at first was mainly manned by Soviet volunteers and under Soviet control.

The SB could outpace the fiat CR.32 and Heinkel He 51 biplane fighters of the nationalist forces, and was therefore difficult to intercept, with dives from high altitude being the only way to intercept the SB. On 29 May 1937 two SBs attacked the German pocket battleship Deutschland, mistaking it for the Nationalist cruiser Canarias, killing 31 and injuring a further 83 German sailors. In June–July, a second consignment of 31 SBs were received, allowing Grupo 12 to return to full strength, and a new unit, Grupo 24, to be established. The delivery of Messerschmitt Bf-109s to re-equip the German condor Legion meant that the SB could no longer evade Nationalist fighters by sheer speed, and losses rose.

A third and final batch of 31 SBs arrived in June 1938, allowing operations to continue, although losses continued to be high. By the time the Civil War ended in March 1939, 73 SBs had been lost, 40 of them to enemy action. Nineteen SBs were taken over by the Nationalists, and used to form a bomber squadron. Although some were re-engined with French Hispano-Suiza 12Ybrs engines to aid maintenance, they were still subject to spares shortages, and in April 1943 only three were airworthy. When Junckers Ju 88s were received in December 1943, the remaining SBs were used for occasional training flights until withdrawn and scrapped in 1948

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