Whakaotihia te rerenga e whai ake nei: I te haurua tuarua o te tau 1926, i mahi a Berek i te 83rd Infantry Regiment i Kobryn. I te Tihema 1926 i tukuna ia ki te 9th Legions Infantry Regiment, ana i te waa o Mei 1929 - Hepetema 1931, i haere ia ki Wyższa Szkoła Wojenna i Warsaw. Whai muri i tana akoranga rangatira, ko ia te rangatira o nga kaimahi o te 4th Infantry Division, i tu ki Toruń (1931 - 1934), ana i te 1934 - 36, i whakahau ia i te 1st Rifle Battalion i Chojnice. I whakatairangahia ia ki te Koronela i te 1 o Hanuere 1935, i mahi a Berek ki te Polish General Staff (Oketopa 1936 - Hōngongoi 1939). I etahi wiki i mua o te whakaekenga o Poland, i tukuna ia ki Jarosław, ki te whakahau i te 3rd Legions' Infantry Regiment. I noho tonu a Berek ki tana pou tae noa ki te hekenga o Modlin Fortress, i te 29 o Mahuru 1939 (tirohia
Te Pakanga o Modlin).