Mezue ahịrịokwu na-esonụ: N'ọkara nke abụọ nke 1926, Berek jere ozi na 83rd Infantry Regiment na Kobryn. Na Disemba 1926 a kpọghachiri ya na 9th Legions Infantry Regiment, na oge Mee 1929 - Septemba 1931, ọ gara Wyższa Szkoła Wojenna na Warsaw. Mgbe ọ gụsịrị akwụkwọ ndị isi ya, ọ bụ onye isi ndị ọrụ nke Ngalaba ndị agha nke anọ, nọ na Toruń (1931 - 1934), na 1934 - 36, o nyere iwu na 1st Rifle Battalion na Chojnice. E buliri ya n'ọkwa Lieutenant Colonel na 1 Jenụwarị 1935, Berek jere ozi na Polish General Staff (Ọktoba 1936 - Julaị 1939). Izu ole na ole tupu mbuso agha nke Poland, e zigara ya Jarosław, ka ọ chịkwaa ndị agha nke atọ. Berek nọgidere n'ọkwa ya ruo mgbe nkwenye nke Modlin Fortress, na 29 Septemba 1939 (lee
Agha Modlin).