In the 1930s, a rather rapid development of reinforced concrete construction began in the USSR. At the same time, they gradually began to move away from monolithic reinforced concrete in the direction of prefabricated structures. The main advantage of prefabricated structures was the ability to manufacture standard parts at landfills or factories, from which a ready-made structure could be easily assembled on site. The fact that for modern citizens, who are literally surrounded by precast concrete structures, is obvious, in the 1930s it still seemed unprofitable and insufficiently reliable.
Just before the war, the first factories for the production of precast concrete appeared in the country. At the same time, monolithic concrete reigned supreme in the fortification, which made it possible to provide the necessary level of protection for the casemate, but monolithic construction was possible only under ideal conditions, in the warm season. To build a monolithic reinforced concrete pillbox in a short time and under enemy fire was simply unrealistic.
The very first fortifications, which were made from concrete blocks, appeared during the First World War. The size of such blocks made it possible to assemble structures from them by hand practically at the front line of the defense. Similar developments also existed in the USSR. For example, a machine-gun pillbox was made up of blocks measuring 40x20x15 cm with holes, which were used to fasten the rows of blocks together dry. Special brackets were inserted through these holes or reinforcement sections were passed. As a result of the assembly, a long-term reinforced firing point was obtained, with a wall 60 cm thick and a casemate 140x140 cm. The covering of such a pillbox was made of logs or rails, a ground pad and the same blocks.
Prefabricated reinforced concrete machine-gun pillbox on the Borodino field, photo by Anatoly Voronin, warspot.ru
But this design had its obvious drawbacks: the assembly of such a structure from more than 2 thousand blocks with a total weight of more than 50 tons required 300 hours of working time. Also from such blocks it was impossible to build a pillbox for an artillery gun. Initially, when creating defensive lines, they were mainly guided by the construction of monolithic structures and bunkers, however, for monolithic bunkers, building materials (crushed stone, sand, reinforcement) and concrete mixers were needed directly at the work site, as well as teams of qualified concrete workers. The production and pouring of concrete mixture had to be carried out in compliance with all technologies. And for the construction of bunkers, not only wood was needed, but also qualified carpenters, sometimes there was neither one nor the other on site.
Therefore, after the start of the war in July 1941, the country decided to intensify the production of prefabricated reinforced concrete pillboxes. Already on July 13, 1941, the State Defense Committee ordered the people's commissariats of the building materials industry, for construction, the Glavvoenostroy under the Council of People's Commissars of the USSR, as well as the Moscow City Executive Committee, to produce 1800 sets of prefabricated reinforced concrete pillboxes. In order to create fortification barriers, factories and enterprises of the Moscow region, Leningrad, Ukraine were tasked with producing 50 thousand metal hedgehogs. By mid-August 1941, 400 sets of pillboxes and 18 thousand metal hedgehogs were produced in the country by a centralized order.
However, the rapid development of the situation at the front posed serious problems for Soviet industry. It was necessary to switch to the widespread use of prefabricated construction as soon as possible, to organize a preliminary centralized procurement of structures and parts for subsequent installation on the defense lines. As in other sectors of the national economy, it was necessary to seriously simplify construction, move on to finding and using local material and technical resources. At the same time, the situation at the front forced the leadership of the USSR to start building defensive lines on a wide front and to a great depth, which was very difficult in the emerging realities.
Construction of defensive lines near Moscow
In general, the GKO decisions given on July 13 and subsequent decisions on the centralized production of reinforced concrete products intended for defense construction were not fulfilled, which was due to a lack of cement. There is nothing surprising. Of the 36 plants of Glavcement, which were part of the People's Commissariat of the Building Materials Industry, 22 plants fell into the combat zone and stopped production. If back in May 1941 the production of cement in the Soviet Union was 689 thousand tons, then in August it decreased to 433 thousand tons, in November - 106 thousand tons, and in January 1942 it was only 98 thousand tons. Interruptions in the supply of fuel and materials, transport difficulties complicated the work of 14 cement plants located in the rear.
It can be assumed that in 1941, prefabricated pillboxes were launched into mass production, which were developed by military engineer Gleb Aleksandrovich Bulakhov. These pillboxes were a set of various reinforced concrete beams, which were joined to each other approximately, like a wooden frame, connecting "into a bowl". At the same time, the frame came out double - with external and external walls, between which concrete was poured or backfilled with stone. The construction of such prefabricated pillboxes was completed literally in one day, using the simplest crane, or even manually. The weight of the heaviest element of this design did not exceed 350-400 kg. The pillboxes were also covered with concrete beams, as a result of which a completely concrete casemate was formed inside. At the same time, the thickness of the side and front walls of the bunker was 90 cm, the back side - 60 cm. The double walls did not require the arrangement of a spall - if the shell hit the outer wall of the structure, the concrete did not crumble from the inside.
There were two main types of prefabricated pillboxes from beams - gun and machine-gun. A 45-mm anti-tank gun, the famous forty-five, was to be installed in the gun pillbox. In the machine-gun pillbox, the casemate was relatively small - 1, 5x1, 5 meters, there was also a low door and an embrasure made of special concrete elements with special anti-ricochet protrusions. In the gun pillbox, the casemates were somewhat larger - 2, 15x2, 45 meters, and the set of elements was simpler. Inside, stops were installed for the bipod of the gun, which was actually located inside the embrasure, covering the entire garrison. But from the "gun set" of beams in the Moscow defense zone, construction was also carried out for machine-gun pillboxes equipped with NPS-3 installations. Surprisingly, the width of the embrasure box almost up to a centimeter coincided with the thickness of the front wall - all that remained was to strengthen it by pouring concrete. In addition, with the help of concrete and formwork, the opening was reduced and an armored door was installed.
Scheme of precast concrete pillbox, drawn up by German engineers
However, the age of such structures was short-lived; in the end, they could only get into the album of the design bureau of the Main Military Engineering Directorate. At the same time, the drawings did not "survive" until the new edition of the "Manual on Field Fortification", which was issued in our country in 1943. It can be noted that one of the reasons for this was the large-scale deliveries to the front line of prefabricated sets of wooden protective structures, including bunkers, which were manufactured in numerous timber industry enterprises. Compared with concrete structures, they were lighter, cheaper and did not require the use of concrete, which was in short supply at that time, as well as reinforcing iron.
Today, the only printed source where there is a mention of these prefabricated concrete pillboxes is a German essay, which was compiled with links to an album of drawings captured by the German army on the territory of Crimea. It is worth noting that prefabricated reinforced concrete pillboxes were erected by Soviet troops around Sevastopol. In the defensive areas that were built around the city, there were machine-gun and artillery structures. The authors of the German monograph highly appreciated the Soviet idea. The work noted that with a cargo crane with a lifting capacity of 500 kg, such a pillbox could be built in just 12 hours. Perhaps this figure was taken directly from that same album of drawings.
Soviet specialists spoke highly of these fortifications. Brigadier engineer A. I. Pangksen wrote in his report that when erecting defensive lines near Moscow, builders preferred prefabricated reinforced concrete casemates made of beam elements. Combat experience has shown that reinforced concrete construction is very profitable in the field. According to Pangksen, one reinforced concrete casemate was usually erected in a day, and the payment for its construction was 500 rubles. In addition to pillboxes made of reinforced concrete beams, pillboxes built from large concrete blocks were also widespread. Such blocks perfectly resisted fragments of shells and mines, as well as bullets, but they could scatter like a house of cubes when heavy shells hit them. Another disadvantage was the mandatory presence of an automobile crane at the construction site.
Prefabricated machine-gun bunker on the outskirts of Ryabinovaya Street in Moscow
Unfortunately, very few prefabricated reinforced concrete pillboxes have survived to this day. After the war, such defenses were as easy to disassemble as they were built. Often they were simply "taken away" for spare parts, which were used in the personal and national economy. Many people used reinforced concrete beams of such pillboxes as foundation blocks, and the dismantling of protective structures was carried out not only after the end of the Great Patriotic War, but also continued in the 1980-90s. A significant number of such pillboxes have survived around the Borodino field, where they are mixed with monolithic structures, as well as on the territory of Moscow, where there are 4 prefabricated machine-gun pillboxes and one gun pillbox.
The largest surviving section of Moscow's defense is currently located in the Bitsevsky forest park, on the southern outskirts of the city between Balaklavsky Prospekt and the Moscow Ring Road (MKAD). In fact, we can say that the entire Bitsevsky Park is one huge monument to the fortifications of the city in the autumn-winter of 1941. An extensive system of trenches with dugouts, machine-gun caps, ditches, bunkers and pillboxes is still preserved in the park. The uniqueness of this section is that even now you can see the whole defense sector of Moscow, which has a depth of several kilometers. Some of the prefabricated pillboxes of this section have become monuments, for example, a prefabricated machine-gun pillbox made of reinforced concrete beams with an embrasure NPS-3, located near the Bitsevsky Park metro station. However, not all pillboxes are so lucky. Most of them are abandoned, covered with graffiti and littered with city debris.
Combined machine-gun pillbox with NPS-3 near Bitsevsky Park metro station
