In Soviet service, the new BRDMs were attached on the divisional level and deployed for screening and long-range probing actions. During the 1960s and 1970s, the scout cars were complemented in Soviet reconnaissance battalions by specialized variants of the BMP-1 infantry fighting vehicles, which were able to reconnoiter much more aggressively and engage hostile armor as needed. About 10,000 BRDMs were built for the Soviet Army and another 1,500 for export, primarily to East Germany, where it received the designation "SPW-40P", and the People's Republic of Poland. The vehicle was criticised for its light armour and the vulnerability of its front-mounted engine compartment during combat, as well as its open top, which exposed the crew to enemy fire when operating the weapons systems. This was partly rectified by the introduction of an improved variant in 1958, which had a hermetically sealed fighting compartment and an overpressure system, reducing the threats from fragments and allowing the crew to reconnoiter contaminated environments. However, it remained impossible to operate the vehicle's weapons system from within the hull. This and other shortcomings prompted Soviet engineers to begin work on a new model of the BRDM capable of carrying the same turret as the BTR-60 armored personnel carrier. The latest mark had the engine compartment shifted to the rear and was considerably more mobile; it entered service as the BRDM-2 during the mid-1960s. The earlier BRDM design was redesignated "BRDM-1" in Soviet service and remained in use until the late 1970s, when it was retired.