by J E Kaufmann
The mortar turret blocks were similar, but the turret did not need additional rooms at the lower level for controls and equipment. Below the turret was the first level that comprised the M-3 magazines and a rest area. The lower level included the filter rooms, WC, and storage areas. The mortar turret block was served by about forty men.
The infantry block varied in size and shape and included firing rooms for heavy and light machine guns and one or more anti-tank guns. In many tvrzi there was one infantry block with a turret for twin machine guns. Since the turret did not retract, it had a less complex mechanism that required less space. Normally, the infantry blocks consisted of two levels, like the other blocks. A fosse protected the space in front of the firing crenels. Some infantry blocks only had cloches for observation and/or machine guns. Isolated positions that were not linked to the tvrz by subterranean tunnels had their own usine.
The entrance blocks usually included a truck and troop entrance similar to a Maginot mixed entrance and came in three types. Babi, Poustka, Jirova Hora, Skutina, Adam, and Smolkov had level approaches. The tvrzi of Dobrosov, Bouda, and Hurka had inclined entrances to give sufficient depth for the main subterranean gallery. Finally, Hanicka, Sibenice, and Orel had the least desirable type of entrance that gave access to the main gallery by elevator. No information is available on the plans for the three remaining forts. Almost directly behind the heavy entrance gate was an armored portcullis that rose from the floor. At the point where the corridor leading from the main entrance to the interior curved, there was a second armored door covered by an interior crenel. This arrangement made it impossible for an artillery piece to fire directly at the armored door from the outside. The area between the two armored doors also served as a gas decontamination area. The garrison of the entrance block was housed on the level below the entrance. Normally the entrance was protected by one or two cloches located above it that allowed for all around defense.
The underground facilities were slightly different from the French. Whereas the French tended to place the caserne by the entrances along with the usine, M-1 magazine, and storage facilities, the Czechs put the caserne in a central location among the combat blocks, leaving the other facilities by the entrance. However, the distance between the entrance and combat areas in the Czech tvrzi was generally not as great as in the Maginot ouvrages, which might account for the difference. In addition, the Czech M-2 magazines also supplied the artillery blocks. In the M-1 magazine, the large cells opened directly onto the main gallery. Unlike the French, the Czechs created larger positions in their main gallery for placing explosives. Finally, like most French ouvrages, the Czech tvrzi had a secret emergency exit consisting of a shaft filled with earth and sand that could be cleared by dumping the fill in an adjacent chamber.
In addition to the nine tvrzi on its northern flank, the ZSV XI was also to have received a line of nine independent artillery blocks on its southern flank. Although none of these artillery blocks were actually laid down, the plans show that these positions would have been one-block forts designed as a combination artillery casemate and entrance block.
The entrance would have looked like most standard entrances with an antitank gun and a light machine gun position. The artillery position would have been similar to most artillery casemates with three guns firing to the flank, and a light machine gun position covering the fosse and exposed face of the casemate. The entrance and artillery position were to be fused together and two cloches would have provided all-around protection. Besides the standard two levels, the independent artillery blocks would have included a third level with about half the area of one of the other levels, and situated beneath the entrance.
The blueprints show an entrance side that measured about 20 meters across and presented only about 10 meters of exposed facade. The exposed section of the artillery side measured about 20 meters in length. The thickness of the reinforced concrete walls and roof is not known, but it is estimated as at least Type III.
Five special independent 120-mm mortar turret block positions similar to those of the tvrzi were planned for the support of the nine independent artillery blocks. Apparently no blueprints were drawn for these positions, but like most separate artillery positions, they would probably have required a usine, a filter room, and magazines.
The interval positions between the tvrzi were just as important in Czechoslovakia as in France. However, unlike the French positions, some of the Czech casemates included heavy weapons such as 90-mm mortars. The majority of interval positions were armed with the standard array of machine guns and one or two anti-tank guns. Most of the interval casemates consisted of two levels and included a usine, a filter room, and one to three cloches. Compared to the French, their designs were less standard.
The interval positions, be they casemates for the 90-mm mortars or casemates with a machine gun turret, were classified as heavy works and in many cases were similar to the blocks of the tvrzi. However, to avoid confusion, they will be referred to as interval casemates in the present work. They usually consisted of two levels and included most of the features of the standard infantry block of an tvrz: a usine, a filter room, munitions storage, crews quarters, and food storage. Most comprised one to three cloches and firing positions for anti-tank guns and/or heavy machine guns and lighter weapons. They also had the protective fosse in front of the main firing chambers and a gas decontamination area between the armored doors of the entrances. The casemates were connected to each other by underground telephone and telegraph cables. About 250 of these casemates were built and more were being planned. Over a third had Protection II which means that the roof was 2.0 meters thick, and the thickest wall (facing forward) was 2.25 meters thick. They could withstand a hit by a 280-mm round. Most of the other positions had Protection III and IV that could resist a 305-mm and 420-mm round respectively.
The lighter fortifications included two basic types of bunkers: Model 36 and Model 37. Found in all the defense lines, the simple Model 36 bunker usually occupied the forward positions along the border. It had no armored embrasures, no facilities for the crew, and no observation equipment. There were six variations on the basic model: types, A through F, but apparently only types A, B, C, and E were actually built. All fired forward and were exposed to the enemy's direct fire. At best, they could withstand 75-mm rounds since their walls and roof were usually less than .60 meters thick. The crew of one of these bunkers consisted of two to six men armed with a heavy or light machine gun, depending on the bunker type. Over 850 of these bunkers were completed by 1937.
The Model 37 light bunker was more important than Model 36. It was intended mainly for flanking fires and came in five basic types:
Type A-one embrasure firing to each flank or obliquely to partially cover forward area or rear area depending on the model. Walls and roofs varying from .60 to 1.0 meter in thickness (the first being able to resist 75-mm rounds and the last 105-mm rounds).*
Type B-one embrasure covering a flank and the other firing forward. Walls and roof varying from .6 to 1.2 meters in thickness (the first being able to resist 155-mm rounds).
Type C-single embrasure for frontal fire. Walls and roof .5 meters thick.
Type D-single embrasure for flanking fire, built in pairs to cover each other and obstacles between them. Walls and roof varying from .6 to 1.2 meters in thickness.
Type E-single embrasure for firing forward or obliquely. Walls and roof varying from .6 to 1.0 meter in thickness.
*They came in standard and reinforced types.
Model 37 was not very large, but had more facilities for the crew. It was designed for light and heavy machine guns, and included equipment for observation, such as sights and periscopes, and defensive features such as armored doors and embrasures.
An attempt was made to create an almost continuous line of anti-tank and anti-infantry obstacles that included the now famous steel hedgehog. The concrete hedgehog was used extensively, but, though economical, it was not as formidable as the
steel version. The hedgehogs were usually emplaced in two to three rows. Steel rails embedded in concrete were also used in many cases with a line of steel hedgehogs. Usually wire was strung up between rows of steel rails and other obstacles and sometimes covered entire obstacles. In some places sizable anti-tank ditches with a concrete wall were built. Every tvrz and its component blocks and other positions as well were at least surrounded by wire obstacles. The main line of defense, consisting of casemates and tvrzi, included an almost continuous line of barbed wire anti-infantry barriers interrupted by roads barred by anti-tank obstacles.
Near the border most roads were blocked by concrete barriers built to form chicanes. In addition, preparations were made to block roads and close forest paths.
WEAPONS AND EQUIPMENT
Armament of the Czech Ouvrages 100-mm Howitzer (turret) (casemate) 120-mm Mortar (Mine Thrower) 47-mm Anti-Tank gun 50-mm Mortar 7.92-mm Heavy Machine Gun 7.92-mm Light Machine Gun (Bren Gun) Other weapons used in fortifications 76.5-mm Cannon 90-mm Mortar Turrets Diameter (meters) Gun 4.0 Machine Gun 2.89 Maximum Range (meters) 11,190 11,190 7,500 5,880 800 3,200 3,200 12,500 4,500 Roof Thickness (mm) 400 300 Mortar 2.50 (exposed area including forward armor rotating section about 1.16) Cloches InfantryType N 1.3 (Light machine gun and 50-mm mortar) Type D 1.3 (Heavy machine gun) Artillery Type P 1.3 (Artillery periscope) Cupolas (had no roof periscope like other Czech cloches) Type D 1.3 (Heavy machine gun) Type M 1.5 (Twin machine guns) 400 150-300 200-300 200-300 200-300 200-300
The Czech protection classification system had two more categories than the French system. Most categories were identical to the French, but a comparison indicates that the Czech concrete was stronger.
WORLD WAR II
The incomplete Czech defenses were never tested in combat. Smolkov, Hurka, Bouda, Adam, and Hanicka, begun in 1936, were almost operational by 1938. The only work that remained to be done was the outfitting the combat blocks and the completion of the installation of the interior equipment. Although some cloches were actually installed, no turrets or artillery pieces had yet been delivered. At Orel, Skutina, Dobrosov, and Babi work began only in 1937 and at Sibenice, in early 1938. Thus none of these forts approached completion in the fall of 1938. However, in some of these tvrzi one or more blocks were ready for use. Construction had not even begun on the remaining tvrzi.
Bouda, one of the smallest tvrzi, was one of the few ready before Munich. It received all of its cloches and weapons by early August 1938, with the exception of the 100-mm gun turret. Smolkov, also minus its artillery, was the only tvrz completed in the area where the Germans planned one of their major assaults on the Czech flanks.
At mobilization the Czech First Army was deployed in the critical northern sectors, seven of its divisions in Northern Bohemia and four divisions of the Second Army in Northern Moravia. Most of the Benes Line fell under the command of these two armies, the Czech Maginot Line being under the Second Army. The southern sectors, under the command of the Fourth Army, were defended by a mechanized division, a motorized division, and six infantry divisions. Many of its heavy infantry casemates were still incomplete and independent artillery blocks remained unbuilt. The Third Army in Slovakia had two divisions and the partially completed defenses on the Hungarian border. A special strategic reserve of three mechanized divisions, a motorized division, and an infantry division was deployed mainly in Slovakia.
Given the type of terrain the Czechs had to defend and the size of the German army in the fall of 1938, they had a good chance of putting up an effective resistance. Despite their incomplete state, the existing fortifications could have presented a formidable barrier to the enemy. However, during the Munich Crisis of the fall of 1938, President Benes was informed by his military leaders that the country could not resist longer than three weeks without support from its allies. Thus Czechoslovakia surrendered its border regions, the Sudetenland, to Germany, leaving only the incomplete tvrz of Dobrosov in Czech hands. Early in 1939 the remainder of the country was occupied by the Germans.
German reports on the potential of the Czech defenses were contradictory. Some claimed that the fortifications were much stronger than expected, while others asserted that they would not have presented a serious problem. As it is, the question of the effectiveness of the multi-national Czech army and the Czech defenses is moot.
The Germans proceeded to use some of the Czech bunkers and tvrzi for testing their weapons' powers of penetration. They most certainly studied the design of the tvrzi, comparing it to the data they already had about the French Maginot Line. In the next few years the Germans stripped almost every heavy infantry casemate and tvrz block of its cloche, hauling off their loot for use in German defenses elsewhere. Many of the famous steel Czech hedgehogs also found their way to the Atlantic Wall. Early in 1945 the Germans used the heavy infantry casemates in the Opava- Ostrava area rather effectively against the Soviets. However, the war simply passed by most of the other Czech fortifications.
Tvrz Bouda. S-22a "Krok" - Entrance. 1 light and 1 heavy MG and two cloches (removed by Germans). Note similarity to French mixed entrance, and the protective fosse. (Karol Vasat)
Tvrz Dobrosov. N-S75 "Zeleny" - Artillery Block. One of the few blocks completed at this fort. 3 x 100-mm guns (never mounted) and 2 cloches. The exit is in the fosse near the second pole from the rear. The embrasure in the front of the picture covers the fosse. (Kaufmann)
Right: Tvrz Dobrosov. A section of the only partially completed galleries of the fort. (Kaufmann)
Below: Tvrz Babi.T-S73 - Infantry Block. Unusually large infantry positions with 4 cloches and two flanking firing chambers. The two flanking casemate positions can be seen. Each mounting a 47-mm gun. The four humps on the roof were positions for the cloche. Little else was completed at Babi. (Kaufmann)
Czech Trvz Kornfelzov. Block STM-44 for 2 x 100-mm howitzers in a turret.
Czech Trvz Kronfelzov. Block STM 45, artillery casemate for 3 x 100-mm howitzers.
Type 37 Czech Bunker.
Czech Trvz Plans
Chapter 10
POLAND
BACKGROUND
After the eighteenth century partitions dismembered and obliterated the Polish state, a new Poland was formed in 1919 and inherited numerous German, Austrian, and Russian ring defenses built after 1870. The Germans had fortified Thorn, Poznan and Grudziadz, the Austrians Krakow and Przemysl, and the Russians Grodno, Warsaw, Modlin, and Brest-Litvosk. Some of these fortifications were still equipped with their original armament.
Due to its geographical position, Poland has been involved in many of the conflicts that have plagued Europe throughout the centuries, and its strategic and political doctrines have been determined by its neighbors, Russia and Germany among others. Between the world wars, Poland was sandwiched between Europe's most powerful Fascist and Communist nations. Its large plains seemed to be inviting invasion.
Since the war of independence had sapped its resources, Poland needed time to catch up with its neighbors both economically and militarily. Yet time was a luxury it did not have. The Polish government and the General Staff expected Germany to seek territorial acquisitions to compensate for its losses after the Great War. They knew that the Germans would not be content with the terms of the Treaty of Versailles concerning their eastern border, and that the Treaty of Locarno did not settle the question. The Polish leadership anticipated a demand for the annexation of territory to link East Prussia to the rest of Germany, and a general revision of the border line. In addition, it found the aspirations of the Soviet Union equally disquieting.
Poland tried to insure its security by signing a peace treaty with the Soviet Union on July 25, 1932, and another with Germany on January 26, 1934. In addi tion, it entered into mutual-aid agreements with France and England. However, Poland was fully conscious of the fact that these treaties were not a guarantee of its territorial integrity and that it needed to make military plans as well. Fully realizing that battling on two fronts simultaneo
usly was a losing proposition but a very real possibility, Marshal Jozef Pilsudski sought a viable answer to the Polish dilemma. The solution he came upon was to adopt the French defensive doctrine. However, the French solution was too expensive for Poland's slim resource. There simply were not enough funds to raise a wall of concrete and steel on the borders, so the Polish fortifications were a considerably more modest version of the Maginot Line.
MAJOR FORTIFICATIONS
Eastern Border
Western Border
Coast Defenses
LOCATION
The terrain of Poland's eastern frontier area extended from the rugged glaciated region adjacent to East Prussia to the great Pripet Marshes east of Brest-Litvosk. The marshes, interlaced with many water courses, were difficult to traverse for a modern army and divided the eastern part of Poland into two regions. Between these regions lay the Polish plains that gave the country its name, heavily forested in many places. In the northeast stood Vilno, a city contested with the Lithuanians, and in the southeast, Lwow (Lemberg), the only major city in the area and the nearby Polish oil fields. Also in the southeast, to the south of Lwow, began the foothills of the Carpathian Mountains. The Bug, which ran in a northerly direction, flowed at 150 km to 200 km from the border, constituting the only significant river barrier in the area. From a point near Lwow to Brest-Litvosk, it formed a large swampy flood plain before it turned to the northwest. The area to the east of the Bug was the most lightly populated region of Poland, except for the Lwow region. The watercourses flowing out of the Carpathians to join the Dniestr River, meet it on a very broad, swampy, flood plain that provided the security for Lwow to the south. The tributaries on both sides of the Dniestr also barred the approaches from that direction.