During the Winter War (1939 - 1940), Talvela commanded "Group Talvela" which took part in the Battle of Tolvajärvi. For this success he was promoted to Major General in December 1939, the first promotion to general's rank during the war. In February 1940 Talvela took the command of the Finnish III Corps in the Karelian Isthmus. When the war ended on 13 March 1940, Talvela returned to civilian life. However, once the Finnish-German relations warmed, he was used in semi-official missions to Germany in late 1940.
During the early Continuation War Talvela commanded the Finnish VI Corps in Karelia. From January 1942, when he was promoted to Lieutenant General, until February 1944 Talvela was the Finnish representative at the German High Command. Once back in Finland, Talvela commanded first the Finnish II Corps in northern Karelia until June 1944 when he took over the command of the Group Olonets (in Finnish: Aunuksen Ryhmä). In July 1944 Talvela was sent back to Germany, where he remained until Finland made peace with the Soviet Union in early September 1944. When he was about to depart for Finland, Himmler reportedly asked Talvela to become the head of a pro-German faction in Finland. Talvela refused out of hand.
Talvela was very able and aggressive commander in offense, but he was less well suited to defensive warfare. He was prone to vanity and temper tantrums and his stubbornness made Talvela a very difficult subordinate. He performed best when given independent commands. Talvela was awarded the Mannerheim Cross in 1941.