Czechoslovak border fortifications 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 fortification s 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 . History . 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 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 where used against the Soviet advance from about April the 17th to the 26th , 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 . Current State . Today almost all of the remaining light objects are freely accessible . Some of the heavy objects are also accessible , others may be rented or sold to enthusiasts . A certain number were turned into museums and very few into depots . The " Hanička " Artillery Fort was being rebuilt into a modern shelter for the Ministry of Interior between 1979 and 1993 , but declared unneeded in 1995 . A museum has been created here . Many of the open museums are located between Ostrava and Opava , close to the present Polish border which had been the German border before World War II . Design . 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 hedgehog s , 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 ) .