During the Bulgarian participation in World War I (1915–1918) General Toshev was in charge of the 3rd Army which routed the Russian-Romanian Army in the Dobruja campaign defeating it in the battles at Tutrakan, Dobrich and Cobadin, but after serious conflicts with the German General August von Mackensen he was replaced with General Stefan Nerezov. Toshev was appointed governor of Macedonia. On 25 March 1917 he was promoted General of the Infantry - the highest military post in Bulgaria.