Armored trains and railway guns became a fixture of the fighting in World War 1 (1914-1918) due to the vast networks, and overall maturity, of railways across Europe. As such, the strategy of fielding such types was left largely unchanged by the time of World War 2 (1939-1945) with all of the major powers continuing to invest and support these machines in combat. For the Soviets, this included the OB-3 class and MBV-2 armored trains, though now developed to a more modern standard, and the final major armored train type to emerge from the fighting in the East became the "PB-43".
The PB-43 saw development begin during the early part of 1942 by which point the Germans had already turned on their former allies. In June of 1941, "Operation Barbarossa" was enacted which meant the complete invasion of the Soviet Union by the Axis - an invasion that ran into December of that year exacting heavy losses upon the Red Army. However, the operation was not the knockout punch envisioned by the invaders and the Soviets eventually managed massive counter attacks in response - bogging down the once swift progress along the East Front.
The PB-43 was equipped with no less than four PL-43 artillery wagons of which each car fitted the complete armored and traversing turret of the classic T-34/76 Medium Tank. This component was set atop an armored bunker-type superstructure to provide protection against small arms, artillery, and air attack. The bunker was equipped with point-defense machine guns, typically of the DT series on a flexible ball-mounting. To defend the artillery wagons, engineers added a pair of PVO-4 air-defense wagons which fitted with one or two 37mm automatic cannon, again in armored steel superstructures, wall panels dropping down when the guns were needed. Completing the design was an armored PR-43 (radio-equipped) locomotive needed for drive power attached to a tender (sometimes equipped with 4 x Maxim machine guns for additional flexible air defense). Up to four security/support cars were also towed and these could house ground troops to be used in defense of the train from ground attackers.
Total production of the PB-43 class armored train series reached twenty-one examples of which two were delivered before the end of 1942 with the bulk of production following in 1943. The last unit came online in 1944. The class was used throughout the East Front where the railway network allowed with notable contributions at Kiev and throughout parts of Eastern Europe. Beyond their direct-contact use, the trains were also operated as border enforcement, semi-mobile defense bunkers where needed, and VIP transports serving Stalin himself.
By 1945, the inherent tactical and strategic value of armored trains and artillery wagons waned, largely due to the restrictive nature of trains going only where tracks allowed. In addition to this, the types were largely susceptible to air attack despite their onboard air defense solutions and semi-mobility. As such, Self-Propelled Guns (SPGs) proved the better, more cost-effective ground-based solution - often times operating in concert with air defense vehicles and air support - until the last days of the war. Nevertheless, the contributions of armored trains to the Soviet defense - and ultimate offense - proved critical.