Below is the brief history of the bunkers. It was found on an information board in Zagorze. It provides the story behind the remains of the fortifications in the forest on the eastern edge of Warsaw. Credits for the text go to Hubert Trzepalka from Pro Fortalicium Association.
History of the Warsaw Bridgehead
The Warsaw Bridgehead was a line of defensive positions running from the Narew river in the area of the village of Rynia to the Vistula river near the village of Nadbrzez. It was constructed in order to defend the valuable road and rail hub of Warsaw, as well as the river crossings on the Vistula and Narew in Warsaw, Modlin and Zegrze from attack from the east.
The area near the confluence of the Bug-Narew and Vistula rivers was first used for strategic purposes by the Swedish King Charles X Gustav during the Second Northern War in the years 1655-1657.
During the Partition of Poland, the Russians who were in power over the eastern part of the country fortified the significant locations even further. The fortifications were intended to be strengthened by linking them to a chain of forts to be known as the Warsaw Fortress. But, in 1909, due to changes in Russian military doctrine, the project was abandoned and the dismantling of fortifications begun.
The Warsaw Bridgehead in 1915 - 1918
Between 1915 and 1916 the German Kaiser launched the construction of an extensive bridgehead (German: Bruckenkopf) for the defence of the crossings of the Vistula & Narew from the anticipated counteroffence by the Russian armies. These new fortified positions were based on the range of sandy dunes and marshy woods stretching between the Narew and Vistula. These modern semi-permanent fortifications consisted of several dozen concrete bunkers for artillery observers, heavy machine guns, infantry bunkers, and numerous lightly fortified corrugated steel bunkers. This was complemented by trenches for marksmen and for support trenches as well as barbed wire barriers.
The weakness of the Tsar's armies and the disastrous defeats which they suffered meant that the Warsaw Bridgehead had become unnecessary by 1918 and the decision was made to dismantle it.
The Warsaw Bridgehead in 1920
The authorities of the newly reborn Polish Republic, understanding the military significance of the fortifications which defended the capital from the east, halted the dismantling process and returned them to their intended military purpose in January 1919. In June 1920 faced with the threat of a Soviet offensive, new works on the fortifications as the first line of defence were hurriedly begun. This new line was slightly extended in comparison to the previous German fortifications.
The battles of 1920 demonstrated the weakness of the extensions of the Polish fortifications from a military engineering standpoint. Those which had been built on flat ground failed to halt the advance of the Bolsheviks advancing on Radzymin and Lesniakowizna.
The fortifications were rapidly breeched and it was only the intervention of strong reinforcements which allowed the breeches to be sealed and the positions to be retaken.
The Warsaw Bridgehead in 1940 - 1944
After the invasion of Poland in1939, nearly all the existing German border fortifications were found to be hundreds of kilometers from the new borders with the USSR. Planning decisive movements against France and Great Britain, the Germans were hesitant to leave their newly aguired territories at the mercy of their unreliable ally, the Soviet Union. A new defensive line was quickly marked out based on Narew, Vistula and San rivers. In the north this line was to join with the Eastern Prussian Border Position. Larger fortified brigdeheads were planned for the most important crossings at Rozan, Pultusk, Warsaw, between Debie and Pulawy, near Annopol (...).
The largest and most heavily fortified of these was to be the Warsaw Bridgehead. The construction of the Warsaw Bridgehead, based partly on the fortifications remaining from the years 1915-1916 and 1920, was begun in the spring of 1940 with the building of a communication route and access roads to the sites of individual bunkers. In total in the years 1940-1941, five R-120 observation points, twelve R 514 pillboxes, and two R 501 personal shelters were built on the Warsaw Bridgehead. Construction works were started on a further three or four sites. The heavy concrete bunkers were built at critical points, and comprised the skeleton of the system. Basic defences were provided by field fortifications. These consisted of 65 resistance points with more than 951 infantry bunkers, 45 artillery observation points, and 85 positions for howitzers and anti-tank guns. This defensive line was further protected by 115 kilometers of anti-infantry obstacles and 19 tank traps.
In the course of operation Barbarossa, the German attack on Soviet Russia, these new fortifications did not play an important role in the fighting due to their distance from the border, and soon found themselves far from the front. Due to this undisturbed concentration of power, on the 14th of May 1941, the construction of new sites was ordered to be stopped and only those sites which were at advanced stages of construction were completed. Construction was only resumed again in the Spring of 1944, when the advance of the Red Army to the west began to threaten Warsaw. These new construction works were meant to be carried out by non-combatant units and civilians. On the 28th of July, the advance forces of the Soviet 2nd Tank Army reached the fortifications.
The weakly manned positions were not a significant challenge for the Russians, German forces defending the positions were modest, and in addition, most were forced to defend the line on the approaches to the positions in order to maintain continuity with the forces defending Podlasie.
The lack of significant manpower coupled with the lack of anti-tank support, poor communications, and the low morale of the German troops who had been steadily pushed back from Wilga and Garwolin, inevitably lead to catastrophe.
On the 29th of July 1944, the Russians flanked the main forces of the German 73rd In fantry Division holding the area between the Kolbiela and Siennica from the west. Two armoured brigades (in total about 80-90 T-34/85 tanks) rapidly broke through the positions at Okoly, in the process destroying the armoured train, and swung around to the rear of the 73rd capturing it's commander, General Fritz Frank.
The German forces retreated leaving the unmanned positions at Swieto and Wiazowna undefended. Simultaneously, a Soviet motorcycle regiment broke through the defences atWygoda, taking Karczew. The Germans retreated to Otwock, and next to the Western banks of the Vistula.
By the 31st of July 1944, the Russians had reached the Zerzen-Miedzylesie-Pohulanka-Sulejowek line, where the German 73rd Infantry Division and numerous support units had managed to hastly prepare a defensive position, which they held until mid-September 1944. The breaking of this line on the 10th of September by the Polish Tadeusz Kosciuszko 1st Infantry Division near Miedzylesie and the loss of Praga lead to a German rout and the abandonment of the remaining fortifications of the Bridgehead. Deprived of its strategic function, the Bridgehead was surrendered without a fight in January of 1945.
The majority of bunkers were demolished most likely immediately after the front had crossed them to prevent their later use by the Germans if the strategic situation were to change. In later years, the remains of the fortifications slowly fell into ruin: they were stripped of their equipment, unexploded shells were detonated inside them, and they became filled with trash. The most well-preserved sites of the Warsaw Bridgehead are the two southern most bunkers at Dabrowiecka Gora. After renovation works, they have become a fascinating open-air museum.
By Hubert Trzepalka
Pro Fortalicium Association
"Warsaw Bridgehead" Chapter
More info at: www.profort.org.pl