Nowadays we associate The Fortified Front of Odra-Warta Rivers mainly with the biggest in Central Europe bat reserve. Thanks to the constant moisture and temperature (ca. 8-10°C) about 300 000 bats of 12 species overwinter here from October till April.
But what happened here before?
After the World War I Germany was military limited – no strong military machines and max. 100 000 soldiers (Poland was stronger than Germany – 350 000 soldiers). On the strength of the Treaty of Versailles Germany lost Alsace and Lorraine for the benefit of France.
Although it was forbidden, Germany wanted to launch an attack on France to get Alsace and Lorraine back. However Poland formed an alliance with France, so the plan started to be too dangerous. If Poland helped France, Germany would have to fight on two fronts.
That’s why Germans started to build some fortifications at the end of the 1920s. They built them along the east border of Germany (now there is Poland). At the beginning only water barriers (dams, movables bridges) and small bunkers were built. Than in 1933 Hitler came into power, changed the plan and decided to build 3 underground connected bunker systems. Following bunker systems were built between 1934 and 1938: Pomeranian Wall (Wał Pomorski) in the north; Oder Position (Umocnienia Odry) in the south; The Fortified Front of Odra-Warta rivers (Międzyrzecki Rejon Umocniony – MRU) in the middle (you can visit it here).
Hitler said officially, that he needs workers and building materials to built a motorway, but in fact the workers were building secretly the bunker system (Now it is the motorway A2, that was built or rather finished by polish workers in 2012. You can see it not far from Boryszyn Loop, between the villages Lubrza and Boryszyn).
The underground tunnels (in total 30 km) interconnect about 20 bunkers. Every bunker consist on e.g.: flamethrower, mortar, copulas with weapon or communication shaft (10 – 40 m high – at our loop 18 m high). The underground system was supposed to be an independent and a self-sufficient city with railway stations, machinery rooms / engine rooms (electricity), barracks, workshops, ammunition stores, toilets, bathrooms, shafts, stairwells, etc.
In 1938 the building was stopped. Hitler changed his plans. Germany was stronger than Poland and Hitler started to plan the World War II.
During the World War II the bunker system wasn’t as used as it was in plan before (It was rather empty). That’s why the Soviet army had no problems to win. It took only 3 days to be broken…