In Soviet Union from the beginning of the Second World War and till the end of 1941 armored trains were intensively manufactured. As a rule, they were built on the locomotive and car-repair factories, and in various railway depots from the improvised materials and accessories. Very often parts of the tanks broken in fights were applied to construction of armored trains. From a few tens of the built armored trains the main part was of the OB-3 type (facilitated).