As a boxer he won silver medals at the 1936 Olympic Games in Berlin and 1937 European Championships, and fought professionally in 1938–39.

During World War II, after the Soviet invasion of Estonia in 1940, Stepulov, an ethnic Russian, became a collaborant in the so-called people's self-defence (RO).

In 1938 he turned professional and fought in Finland, Sweden, Denmark and Germany with a record of 5 wins (4 by knockout), 5 losses and 1 draw.

[2][5] During his boxing career Stepulov served in the Estonian Army as a private, and was promoted to corporal for his Olympic success.

In 1945 he returned to Estonia, claiming to been meanwhile a Soviet spy, and took odd jobs as a factory worker, turf cutter, lumberjack and boxing coach and referee.