by J E Kaufmann
The southern border encompassed the Carpathians that extended into Slovakia, forming parallel ranges that presented a formidable obstacle to an aggressor from either direction. The old fortresses of Przemysl, Jaroslaw, and Krakow were strategically located in defensible positions to block an invasion coming out of Slovakia.
North of Warsaw and east towards Grodno, the Polish Plain merged with the morainic regions of East Prussia. The area was heavily forested with numerous lakes and marshes. The Narew River, a tributary of the Bug, also created a marshy flood plain that paralleled the East Prussian border. The Polish Plain, itself a product of glaciation, covered most of the country. Broken by few hills, it consisted mostly of low and level to rolling terrain with many open and wooded areas. It was ideal terrain for army maneuvers. The Vistula, sometimes called "Poland's Mississippi," presented a large, formidable obstacle. It is navigable from the San, one of its tributaries in the south, to its mouth. It was subject to flooding after heavy rains in the Carpathians, and when it overflowed onto its flood plain, it became one of the country's greatest defensive assets. Some fortress cities like Warsaw and Modlin sat on a high terrace overlooking the river, safe from inundation.
On the western frontier of Poland there were fewer natural defenses. Krakow in the southwest corner and the Carpathians and their foothills in the south created a strong barrier. Just to the west and northwest lay Black Silesia, Poland's industrial heart, that relied on the small hills in the area for defense. The Warta River, which flowed north to Poznan, did not form a major barrier even though its valley was marshy. Most of the border area facing Germany consisted of open plain with few obstacles beyond the moraines of Pomerania that constituted part of the Polish Corridor.
The most important element in Poland's favor was the lack of modern roads. Winter snows and heavy summer rains easily turned the old roads and the surrounding fields into a quagmire. This could be a serious advantage for an army that still depended heavily on the horse against a mechanized enemy. Unfortunately, Nature did not favor Poland in September of 1939.
HISTORY
After several visits to the French fortifications, the Polish military engineers returned to Poland full of new ideas and soon formulated new projects. As a result, the Polish fortifications exhibit a strong French influence. The first concrete fortifications in the new Poland went up between 1924 and 1925 on the Vilna Defensive Position. On July 29, 1929, the first tests on bunker resistance capacities were carried out at the testing grounds of Modlin.
The defensive preparations on the border with the Soviet Union began in 1926, when the General Inspectorate of the Armed Forces was established. The first plan of operations, formulated in 1928, comprised blueprints for a defensive line to protect eastern Poland. The mission of this line was to buy time for the field army to mobilize by defending the lines of communications, and by making the most of the surrounding terrain.
In 1934, Poland, which still considered the Soviet Union its greatest peril, concentrated all its attention on the eastern border. Nonetheless, the border with Germany was not neglected. Work began there in 1933, but only the Silesian border received heavy fortifications. Military planning changed as relations with Germany deteriorated during the second half of January 1939. The major building effort was then transferred from the eastern to the western front. Unfortunately, time ran out before the army could fully implement its plans.
In 1938, when Poland took advantage of Hitler's takeover of Czechoslovakia to occupy Zaolz, its military engineers came across the Czech fortifications. The Poles not only inventoried these defenses but, like the Germans in their "Protectorate," they used artillery pieces to test as many as 231 bunkers.
Operation "Direction West" (Kierunek Zachod) was formulated between 1928 and 1935 under the leadership of Marshal Jozef Pilsuldski and the Chief of the Polish General Staff, Brigadier-General Janusz Gasiorowski. The latter saw to the installation, among other things, of a series of concrete company-size strong points equipped with heavy arms and artillery along the main communication lines leading to the heart of Poland. The mission of these strong points was to hold the enemy until the arrival of his heavy artillery. This delay would buy time for the army to prepare behind the lines. Edward Rydz-Smigly, heir to Pilsudski's policy and appointed as Marshal of Poland on November 10, 1936, was forced to juggle his limited resources between the eastern and western border and simultaneously attempt to modernize the army.
In February of 1939, when German aggression became increasingly likely, Marshall Rydz-Smigly advised Brigadier-General Waclaw Stachiewicz, Chief of the General Staff of the Polish Army, to implement plan "Direction West." The implementation was hastily carried out to meet the realities of the moment. The first line of defense was established, and the units were assigned to specific armies and commands. On March 3, 1939, the commanders of the armies received a portion of their instructions dealing specifically with their own sectors. They proceeded to plan the defensive lines with a deadline for the completion of the preliminary work set for May 31, 1939.
As a result of the shift in focus through the 1930s, the Polish defensive lines acquired a fragmented character, failing to become a continuous line of fortifications. The onset of the war on September 1, 1939, terminated the building effort.
DESCRIPTION
The schron was the basic building block of the Polish defenses and came in various types. One of the most common types of schron was the one-room machine gun shelter or bunker.' Its configuration was determined by its mission. The entrance of these small blockhouses was protected by a wall about a meter long or more. On the interior walls there were niches for a hand-operated fan, a coal-burning stove, and a supply of ammunition.
Another very common type of schron was a casemate that mounted machine guns firing to a flank. The weapons embrasures of these small casemates occupied side walls protected by concrete orillons (ears or wings). Some had one embrasure covering one flank and others an embrasure for each flank. The section facing the enemy was covered with earth and the entrances were similar to those of the blockhouses. Due to their small size, these positions had no elaborate facilities. However, their low profiles were not easy targets for artillery fire. Some included an armored cloche for a machine gun that fired across the forefield. This cloche was more vulnerable to artillery than the remaining elements of the position, and for this reason it was separated from the rest of the bunker by an armored gas-proof hatch.
The basic combat position of the fortifications on the western borders was a schron with a machine gun embrasure on one or both flanks that sometimes included a cloche. An earlier, larger, structure included garages for a 37-mm anti-tank gun (Mle 1897), from which the gun was moved to a field position. In a few places there were anti-tank casemates that mounted this type of weapon in an armored embrasure that covered the flank.
After 1937, plans were made to build many positions consisting of armored casemates for 37-mm guns (Mle 37) mounted on an overhead rail. The large defensive positions such as the OWS (Fortified Region of Silesia), Wegierska Gora (Hungarian Hill), and Jastarnia, consisted of fifteen to twenty casemates that housed several types of weapons. They also included schrony with armored plates for heavy machine guns of the Browning 1930 type, similar embrasures for light machine guns, a grenade launcher, and a cloche or half cloche for combat and observation. The crew quarters were not comfortable and had no latrines or other facilities. The bunkers were linked by telephone lines. The larger ones were also outfitted with special horizontally placed steel pipes for light signals in case telephone communications were cut.
Schrony for anti-tank guns and field guns began to appear in 1939. Most served as flanking casemates and were larger than the other schrony. They were designed to shelter both 37-mm anti-tank guns and 75-mm field guns and were to include observation cloches, few of which were actually installed. By the time the war started, many positions were only partially finished.
Sector command bunkers, intended
to shelter the command post of a sector, included an observation cloche with an artillery periscope, and a cupola that was separated from the rest of the shelter by a gas-proof hatch. These command bunkers included communication equipment and special tubes for light signals.
In addition to these positions, some of the older works such as the forts of Modlin were restored. New schrony were added at Modlin to extend the defenses of the position. The armament of the Modlin forts included a variety of weapons, some in revolving cupolas and others in open emplacements or casemates.
Various anti-tank and anti-infantry obstacles were used, including rows of steel rails, barbed wire, obstacles to close off roads, local demolitions, and devices for flooding wherever practical.
1. The Eastern Border
The fortifications on the eastern border rested on the Wilia, Niemen, Prepec, Stycz, Styr, Narew, Serwecz, Szczara, and Prut rivers. There were six sectors: Wilno (Vilna), Lida, Baranowicze, Polesie, Wolyn, and Podole. The main Soviet thrusts were expected to come from Belrus in the direction of Warsaw, Baranowicze, and Bialystok and from the Ukraine towards Wolyn. The largest fortifications were built in the Polesie Sector, which was considered to be the most important. It was the longest sector, covered the most difficult terrain, and lacked roads. The fortified line incorporated the water courses where a system of dams and weirs were created to impede the enemy's progress. Only 800 of the planned 1,400 water obstacles were actually built.
The fortifications projected in 1936 for the Polesie Sector were not completed. They were to have included six 75-mm guns and eight mortars and numerous heavy and light machine guns east of Chelm. Only four schrony were nearly completed, lacking only their interior fittings because the original plans had to be modified to meet the limitations imposed by a tight budget. Each schron consisted of two blocks, A and B and a linking tunnel, a rarity in Poland. The two blocks lay at different levels on the terrain. Only three tunnel systems were completed, including the one to the mortar casemate. Most of the blocks consisted of two to three levels, had D or E strength, and mounted a cloche. The largest schron was for four mortars, had C strength, and accommodated a crew of 26 men. All the positions had a complete set of facilities but no usine. Mines were to be added to the usual array of anti-tank obstacles. When the war began, these blocks were still incomplete and remained unoccupied.
The fortified sector of Baranowicze was supposed to receive positions with a revolving turret for a 37-mm or a 75-mm anti-tank gun. However, the armored elements were not yet mounted when the army suspended work on this sector in 1939.
2. The Western Border
Much of the work on the western border was done late in the 1930s except on the largest sector of permanent fortifications known as the Fortified Region of Silesia (Obszar Warowny Slask or OWS). It was built between 1933 and 1939 along a wide semi-circle encompassing Chorzow, Katowice, and Milkow. The mission of the OWS was to secure the Central Industrial Region, the industrial heart of Poland located in Upper Silesia. This fortified region stretched for over 60 km and included 160 positions.
Since Upper Silesia was a highly industrialized area, most of the positions were located in urban settings. The line consisted of the defensive points (punkty oporu or PO) of Bobrowniki, Lagiewniki, Dabrowka, Godula, Nowy Bytom, Szyb Artura, Radoszow. The POs of Niezdara-Tapkowice and Kotulowiec were still in the planning stage by the time the war broke out. In 1939 new field fortifications for anti-tank guns were built to strengthen the OWS line. Their armament consisted of anti-tank guns.
In addition to the various types of blockhouses and casemates, the OWS included independent blockhouses or samodzie]ne schrony bojowe whose weapons covered all directions. It also comprised heavy flanking gun casemates or ciezkie schrony tradytoryjne armed with 75-mm guns to defend the area between POs and all roads in the environs. There were two of these gun casemates at Bobrowniki, Hill 305, that mounted two 75-mm field guns in individual gun rooms. The guns were placed on a rotating platform that allowed them to fire from two different directions. These casemates had complete facilities including a usine, filters, rest area, munitions room, and an observation cloche. Other schrony that housed the command post, machine guns, 37-mm (model 37) guns, and observation, supported the position.
Seven other positions and another fortified region, primarily made up of the coastal defenses, guarded the border with Germany. The Wizna Position, located near the confluence of the rivers Biebrza and Narwa, near the town of Wizna, faced the expected direction of attack from East Prussia. Built in 1939, it was a strong fortified position 9 km in length, whose framework was made up of eleven schrony armed with heavy machine guns, 75-mm guns, and cloches.
The Golancz Position was to rest on the lakes just to the north of Poznan. Originally in the region of Wagrowiec, Golancz was to consist of twenty schrony. In a note dated August 11, 1939, General Tadeusz Kutrzeba revised that number to twenty five. However, by September 1, 1939, only fifteen were actually built: nine casemates for a heavy machine gun (CKM) with frontal fire, three with a flanking CKM, two with CKMs covering each flank. All these structures had resistance Strength B.
The Prosna River Line in the region of Kalisz lay to the southeast of Poznan. The original plans called for twelve schrony but later changes raised this number to thirty-three. However, only nineteen were actually built: one for observation, five for CKM with frontal fire, eight for a CKM firing to a flank, and five with CKMs firing from embrasures on both flanks.
The Pszczyna Line, intended to support the OWS Line in the defense of Upper Silesia, was to extend from Czestochowa, through the Silesian defensive region of the Tarnow Mountains, to Chrzan6w and Katowice. This line was to incorporate the Pszczyna, Bielsko Biala, Zywiec, and Rabka positions. Fifty-six schrony were originally planned for the area of Pszczyna. The building effort in the Pzsczyna Line was concentrated in the center of the area of operations of the Krakow Army. Fifty-six schrony were originally planned for the area of Pszczyna, on the terrain assigned to the 6th Infantry Division. However, when the order came to strengthen the areas of Rybnik and Zar, this number was dropped to twenty-four. By the time the war broke out, only fourteen schrony were actually built from a distance of 6 km from Pszczyna, to the forest north of it. Only initial excavations were done in the area south of Pszczyna in the direction of the village of Goczalkowice.
The remaining positions covered the northern front with Germany. In the Polish Corridor, which fell under the command of the Pomorze Army, preparations were made to cover an attack from two directions: from East Prussia towards Torun and Wloclawek and from West Pomerania towards Gdansk and Bydgoszcz. The defense plans for the Pomorze Army included the construction of a fortified line supported by field positions in the Bydgoszcz Bridgehead. In the region under the jurisdiction of the 9th Infantry Division, near the town of Koronow, the Koronow Lake Position was supposed to rest on the lakes in the area. Only thirteen schrony of the thirty originally planned were completed by September 1, 1939. Two of these had not yet been covered with the protective layer of earth. Fifteen more schrony were in various stages of construction, most only in the initial stage.
The Modlin Army defended the Mlawa Position, the regions of Lidzbark Welski, Mlawa, Krzynowloga Mala, and the main line that rested on the Vistula and Narew rivers. It was assigned the task of slowing down the enemy advancing from Eastern Prussia toward Warsaw, Nidzica, and Modlin. A defensive line was planned for the vicinity of Mlawa which was occupied by the 20th Infantry Division, and blocked the most direct approach from East Prussia to Warsaw. Of the ninety-three schrony- mostly casemates-projected for the Mlawa Line, only forty neared completion or were finished when the war broke out. Others were in the early stages of construction.
3. The Coast Defenses
The small Polish coastline fell under the jurisdiction of the Fortified Region of Hel. The focus of interest in this area was the Hel Peninsula, which defended the seaport and naval base of Gdynia, Poland's "window on the world."
Between 1933 and 1935, Second Lieutenant Heliodor Laskowski directed the construction of a four-gun coastal battery armed with long-range 152.4 mm Bofors guns. In addition, there were three two-gun batteries mounting 75-mm guns on barbette mounts including munition magazines, casernes, storage rooms, and so on. Four large shelters for torpedoes and artillery munition were also built to meet the needs of the navy. Another battery, similar to Laskowski's, and a battery for 320-mm guns, were also planned, but funds ran out before these guns could be acquired.
The Military Transit Depot at Westerplatte, in Danzig (Gdansk) was guarded by five concrete blockhouses that served as sentry posts and had 0.30 meter thick walls. Three machine guns were mounted on the roof.
In 1939 the peninsula was blockaded from inland with the defensive strong point of "Jastarnia." Plans for this position called for seven objetkty, bunkers or casemates, in three successive lines. However, there was only enough time to complete three large and one small casemate, and pour the foundations of the remaining three.
These positions were characteristic of the Polish school of fortification. They were rather small, well integrated into the terrain, tied to each other with a carefully planned field of fire, and supported by field fortifications. Gun emplacements giving flanking interlocking fires were also characteristic of this school. Earth covered the front walls of the casemates for camouflage and protection. Frontal defense was assured mainly by heavy machine guns placed in cloches embedded in the roofs. Each casemate was to mount one or two cloches that, unfortunately, were not completed in time for the war. The schrony built next to the railroad also held 37-mm anti-tank guns.
