In January 1940, Timoshenko took charge of the Soviet armies fighting Finland in the Soviet-Finnish War. This had begun the previous November, under the disastrous command of Kliment Voroshilov. Under Timoshenko's leadership, the Soviets succeeded in breaking through the Finnish Mannerheim Line on the Karelian Isthmus, prompting Finland to sue for peace in March. His reputation increased, Timoshenko was made the People's Commissar for Defence and a Marshal of the Soviet Union in May, replacing Stalin's crony Marshal Voroshilov as the Minister of Defence.