In 1926 the Polish authorities examined the condition of the border areas, especially of the fortifications built by the Germans and the Austrians during World War I. During the Inter-War Period a lot of these constructions were used by Poland for building fortifications on the Polish-Soviet border. So, Poland based its defence system on the eastern borders upon many fortified structured left from World War I.
Lots of the German constructions were renovated and modernised, often the Polish erected their own buildings nearby. One of the peculiarities of the Polish pillboxes was the extensive use of armoured turrets. A Polish observation bunker M1936 is located in the territory of the Historical and Cultural Complex Stalin Line. Its inside diameter is 100 cm , wall thickness is 12 cm, and 6 embrasures give the possibility to watch and deliver fire at close range. This observation bunker was demounted from a command-and-observation post near the Zaosye village in Baranovichi region.
It should be noted that the Polish authorities divided the fortified zone on its eastern border with the USSR into 6 main regions, which were “Vilno”, “Lida”, “Baranovichi”, “Polesye”, “Volyn” and “Podolye”. Special attention was paid to Baranovichi region, because it had to impede the movement of the Soviet troops, start a long trench war and protect the route to Warsaw.
But this fortified zone was never used. On 1 September of 1939 Nazi Germany invaded Poland, starting thereby the Second World War. The Polish Government was not able to protect the country and fled to Romania, leaving its people and demoralised troops to their own devices.
Under such circumstances the Soviet government gave the order to cross the Polish-Soviet border to protect life and property of the people from West Ukraine and West Belorussia. That is why on 17 September 1939 the troops of the Kiev and Belorussian Military Districts started the so-called Liberation campaign. On the same day the fortified district and the town of Baranovichi were taken without striking a blow.
Soon after the liberated territories of West Ukraine and West Belorussia were returned back to the USSR (with a total area of more than 190 square km, and with a population of more than 12 million people) David Lloyd Jeorge, a former British Prime-Minister, was writing to a Polish ambassador in London in autumn of 1939 that “the USSR took control of the territories which did not not belong to Poland because these territories had been forcefully annexed by Poland after the First World War”.