SK Slezská Ostrava began to compete with other teams in the league system in the spring of 1923. It started in the lowest division "(III. třída župy)" and was promoted to the higher division the same year. It took, however, some time for the club to reach the highest divisions of football in Czechoslovakia. In 1934 the club won promotion to the Moravian-Silesian Division, one of the highest leagues in the country. The promotion made SK Slezská Ostrava a popular team in the city and public interest was rising. The 1935 derby against Slovan Ostrava was watched at "Stará střelnice" by 5,400 spectators.