After the German occupation of Poland in 1939, the club was officially discontinued but unofficially was simply renamed Bismarckhütter SV 99 and joined the Gauliga Oberschlesien in 1941. The club was officially re-established after the war. In 1947 Ruch won the regional championships. In 1948, under communist pressure (Stalinisation), the club was renamed Unia Chorzów, in 1955 it became Unia-Ruch, and finally in 1956 returned to the name Ruch. As Unia the club finished third in the first season of the reactivated national league in 1948 and in 1950 as the second team. In 1951 the club won the reactivated Polish Cup edition and were rewarded with the title of the National Champions (even though they were only sixth in the league). The next two years the club also won the title, first in 1952 after final against Polonia Bytom, another local bitter rival, and in 1953 after finishing the league on the top position. The most renowned player of that era was Gerard Cieślik, who dedicated his whole life to the club and became its icon.