Unlike other world powers of World War 1 (1914-1918), the Russian Empire placed a premium on armored trains as part of its ground force. This was something of a necessity for the Russians as their road infrastructure was lacking in the industrialized world during the period and moving men, machines and supplies for mobilization in the Great War was going to be by railway - a strength of interior Russia. Varied interim and standardized concepts then emerged in the fighting and most saw their bloody days in the Civil War that pulled the Russian Empire out of the war. Consequently, the Russian Empire fell and was reborn as the Soviet Union whose engineers continued the design and development of the armored train into the 1930s.
The Legkaya Broneploshadka PL-37 was a standardized design for a "light artillery wagon" - a single car laden with cannon armament and machine guns intended to serve along with infantry cars and an armored locomotive in action. It was used by Soviet train battalions early in World War 2 (1939-1945) and production of the class - handled by the Krasniy Profintern Platn of Bryansk - numbered about 24 units in all from 1939 to 1941. Their underlying configuration was conventional, retaining the same capabilities as the rail car it was formed from. The chassis was made up of a 55-ton Diamond brand twin-axle truck arrangement. To this was added a steel superstructure and a pair of large turrets to field cannon armaments. Even the wheels were protected over through low-lying skirt armor. The internal volume of the superstructure at center was taken up primarily by ammunition stores which made for cramped conditions for the crew - which numbered thirty personnel to manage the various stations aboard the car. An armored tower for the commander was fitted amidships with glass visors and a PTK periscope to aid with observation, artillery direction and general situational awareness.
The car weighed in at some 77 tons under full loads and featured a running length of 48 feet, 2 inches, a width of 9 feet, 9 inches and a height of 14 feet, 5 inches. Armor protection ranged from 0.78 inches along the sides of the superstructure to 0.59 inches along the roof line.
Key to the PL-37's design was its armament of 2 x 76.2mm Mod. 1902/30 field guns, each gun and its applicable mounting hardware held in traversable turrets at the front and rear ends of the car. 560 x 76.2mm projectiles were carried in High-Explosive (HE) and Armor-Piercing (AP) flavors to suit the mission need. The Soviets found out that their 76.2mm guns were quite effective against many forms of German armor so the Mod. 1902/30 did not disappoint in its intended role. Beyond the cannon armament, the PL-37 was also given a battery of 6 x 7.62mm Maxim water-cooled machine guns - two along each hull side and the remaining pair as coaxial mounts in each turret. These weapons could provide suppression fire of infantry forces attempting to overtake the train or support allied offensives as needed. The water-cooled nature of the machine guns ensured proper cooling of the barrel so long as a water supply was available.
Armored trains still held some battlefield value in World War 2, particularly in hard-to-reach areas of the Russian Empire. However, as the strike aircraft threat continued to grow throughout the conflict, the value of the armored train was realized and, in turn, dwindled in its active use. Armored trains were relatively easy pickings for incoming dive bombers for their speeds were contained and their paths constrained to the available tracks. Knocking out a whole bridge could render the reach of armored trains useless or downright limited overall. An incoming bomber need only content with defensive machine gun or cannon fire as it swooped down with machine guns, cannon fire, drop bombs, or rockets of its own. While the interwar years marked the technological apex of the armored train, World War 2 served as its swan song though the Soviets kept a stock of such pieces for security purposes into the Cold War years.
Many Soviet armored trains fell in the opening salvos of the German invasion of the East.