At the beginning
This project was created as the initiative of longtime friends. Our goal is to open renovated bunkers of Czechoslovak fortifications in the area of Bratislava to public in form of museum.
The Czechoslovak government built a system of border fortifications, as well as some fortified defensive lines inland, from 1935 to 1938 as a defensive countermeasure against the rising threat of Nazi Germany that later materialized in the German offensive plan called Fall Grün. The objective of the fortifications was to prevent the taking of key areas by an enemy (not only Germany but also Hungary) by means of a sudden attack before the mobilization of the Czechoslovak army could be completed, and to enable effective defense until allies (Britain and France and possibly the Soviet Union) could help.
With the rise of Hitler and his demands for unification of German minorities (the Sudeten Germans) and return of other claimed territories (the Sudetenland), the alarmed Czechoslovak leadership began defensive plans. While some basic defensive structures were built early on, it was not until after conferences with French military on their designs that a full scale effort began.
A change in the design philosophy was noticeable in the “pillboxes” and larger blockhouses similar to the French Maginot line when the massive construction program began in 1936. Construction was very rapid, and by the time of the Munich Agreement in September 1938 about 20% of the heavy objects and 70% of the light objects were completed, however most of the remainder were near completion and would have been functional despite missing certain heavy armaments in some structures. The total planned (and nearly all mostly completed) was 10,014 light pillboxes and 264 heavy blockhouses (small forts).
The original plan was to have the first stage of construction finished in 1941-42, whilst the full system should have been completed by the early 1950s.
After the German occupation of Czechoslovakia border regions as a result of the “Sudeten crisis”, the Germans used these objects to test and develop new weapons and tactics, plan, and practise the attacks eventually used against the Maginot Line and Belgium’s forts (the most notable is Fort Eben-Emael), resulting in astounding success. After the fall of Belgium, France and the low countries, the Germans began to dismantle the “Beneš Wall”, blowing up the cupolas, or removing them and the cannon/MG embrasures, some of which were eventually installed in the Atlantic Wall against the Allies.
Later in the war, with the Soviet forces to the east collapsing the German front, the Germans hurriedly repaired what they could of the fortifications, often just bricking up the holes where the cannon/MG embrasures once were, leaving a small hole for a machine gun. The east-west portion of the line that ran from Ostrava to Opava which is a river valley with a steep rise to the south, became the scene of intense fighting. It is unknown how vital those fortifications were to German defense, but after hurried patching of some buildings leaving holes for machine-gun nests they were used against the Soviet advance from about April 17–26, 1945.
During World War II the Germans had removed many armored parts like domes, cupolas and embrasures from the majority of the objects. Some objects became subjects of German penetration shells or explosives testing and are heavily damaged. In the post-war period, many of the remaining armoured parts were scrapped as a result of a loss of their strategic value and general drive for steel.
After the war they were further stripped of useful materials, and then sealed. A couple of the large underground structures continued to be used long after as military hardware storage, and some still are to this day, by the now once again independent Czech military, 60 years later.
The basic philosophy of the design was a mutual defensive line, that is, most of the firepower was directed laterally from the approaching enemy. The facing wall of all the fortifications, large and small, was the thickest (reinforced concrete), covered with boulders and debris, and covered again with soil so even the largest caliber shells would have lost most of their energy before reaching the concrete. The only frontal armament was machine gun ports in cupolas designed for observation and anti-infantry purposes. Any enemy units that tried to go between the Blockhouses would have been stopped by anti-tank, anti-infantry barricades, MG and cannon fire. A few of the larger Blockhouse, or Artillery Forts, had indirect fire mortars and heavy cannon mounts. Behind the major structures were 2 rows of smaller 4 – 7 man pillboxes that mirrored its larger relatives, with a well protected front and lateral cross fire to stop any enemy that managed to get on top of the fort, or come up from behind. Most of the lines consisted of just the smaller pillboxes.
The fortifications consisted of “Heavy Objects”, which means either isolated Infantry Blockhouses (Casemates) or Artillery Forts (connected infantry and artillery casemates, artillery and mortar turrets, etc.) similar to the French Maginot Line, and “Light Objects” (pillboxes), designated vz. 36 (model 36, the so-called French type) and a more modern vz. 37 (model 37), besides a system of obstacles (e.g. barbed wire, Czech hedgehogs, anti-tank ditches and walls, and also natural obstacles).
The “Light Objects” (pillboxes) were simple hollow boxes with 1 or (typically) 2 machine gun positions, a retractable observation periscope, grenade tubes (small tube that leads outside), hand operated air blower, and a solid inner door at 90* to a steel bar outer door. The machine gun was mounted near the end of the barrel, so that the port hole was only large enough for the bullets and a scope to see through, unlike most other designs where a large opening is used. A heavy steel plate could be slid down to quickly close the tiny hole for added protection.
The “Heavy Objects”, infantry blockhouses (casemates) are very similar to the southern part of the Maginot line, but with substantial improvements (probably reflecting the 6 years since construction of the French line began). Just like the pillboxes, the cannons and machine guns were pivoted at the tip, and this time fully enclosed, protecting the occupants from all but the heaviest of cannons. The fortresses had a full ventilation system with filtration so even chemical attacks would not affect the defenders. Besides grid power, a 2 cylinder diesel engine provided internal power. These fortifications also had full toilet and wash basin amenities, a luxury compared to its French counterpart casemates (however, these facilities were designed to be used only during the combat). While largely hollow with a few concrete walls as part of the structure, each chamber was further divided into smaller rooms by simple brick and mortar walls, with a last gap at the ceiling filled with tarred cork (construction of a few of the casemates stopped before the internal walls were finished).