 Thereafter Mostowicz wrote an average of 2 novels a year.His monthly income is estimated to have exceeded 15,000 złotych, some 2,800 1939 US dollars.During the Invasion of Poland in 1939, Dołęga-Mostowicz was mobilized and served as commanding officer of an outpost defending a bridge over the Cheremosh River at the town of Kuty in southeastern Poland.