Faatumu le fuaiupu lenei: I le afa lona lua o le 1926, na auauna ai Berek i le 83rd Infantry Regiment i Kobryn. Ia Tesema 1926 na toe faafoʻi atu ai o ia i le 9th Legions Infantry Regiment, ma i le vaitaimi o Me 1929 - Setema 1931, na auai ai o ia i le Wyższa Szkoła Wojenna i Warsaw. Ina ua uma ona faauma lana vasega o le ofisa, sa avea o ia ma pule sili o le aufaigaluega a le 4th Infantry Division, na tofia i Toruń (1931 - 1934), ma i le 1934 - 36, na ia faatonuina le 1st Rifle Battalion i Chojnice. Na siitia o ia i le tulaga o le Lieutenant Colonel i le aso 1 o Ianuari 1935, sa tautua Berek i le Polani General Staff (Oketopa 1936 - Iulai 1939). I ni nai vaiaso a o leʻi osofaʻia Polani, na auina atu ai o ia i Jarosław, e pule i le 3rd Legions' Infantry Regiment. Na tumau pea Berek i lona tofiga seia oo i le faamavae o Modlin Fortress, i le aso 29 Setema 1939 (tagai
Taua o Modlin).