One of the major improvements to the Soviet armed forces that came out of the Winter War was the replacement of Kliment Voroshilov by Semyon Timoshenko as People’s Commissar for Defence. Voroshilov had helped Stalin carry out the Great Purge by denouncing some of his military colleagues, and (as I recall) he reversed some of the army reforms that his predecessors had carried out. He also bungled the opening phases of the Winter War, and was eventually turfed out in favour of the more competent Timoshenko. After the Soviets won in Finland, Timoshenko set about modernizing the Red Army.