region apparently failed to provide a secure haven for Polish industry. The idea of the safe triangle came from the thinking of the Polish military strategists during World War I and the Polish—Russian War in 1919–1920. This idea was upgraded during the late 1930s and many of the factories crucial to the war effort got distributed across the country. Moreover, the PZL.37 Łoś, a medium bomber, the factory was successfully moved and reassembled in the easternmost Poland that fell to the Soviet advance after September 17, 1939. In any event, the German dismemberment of Czechoslovakia outflanked Poland from the south and put the majority of COP factories in the direct path of German advance from Slovakia. During the German occupation, most of the factories were converted to contribute to the German war effort. After the war, the COP-initiated industrial enterprises were further expanded and for the most part, continue to function until today. Melchior Wańkowicz, in his 1939 book Sztafeta, emphasized the fact that the quick growth of the COP's towns and cities was not followed by necessary investments in infrastructure, especially schools and housing. As Ilustrowany Kurier Codzienny announced on January 10, 1939, in the first half of 1938, the population of Rzeszów grew by 24%, that of Sandomierz by 29%, Tarnobrzeg by 49%, and Mielec by 58%. Altogether, in the first half of 1938, the total population of all the COP's towns and cities grew by 20%. According to a press release from January 1939, out of 33 towns and cities located at the confluence of the San and the Vistula rivers, as many as 23 needed new schools. See also Sandomierz Voivodeship (1939) Upper Silesian Industry Area Gdynia Polish Coal Trunk-Line Sztafeta References Wiesław Samecki, Ekonomia 3: Centralny Okręg Przemysłowy 1936–1939, Wydawnictwo Uniwersytetu Wrocławskiego, 1998, Economic history of Poland Second Polish Republic Regions of Poland History of Lesser Poland Kielce Voivodeship (1919–1939) Kraków Voivodeship (1919–1939) Lublin Voivodeship (1919–1939) Lwów Voivodeship 1936 in Poland 1930s in Poland Industrialisation Economic planning