 He helped Walerian Czuma organise 1st Kosciuszko regiment at Samara in August 1918 which later formed the 5th Rifle Division in Siberia (sometimes known as the Polish Legion or the Siberian Division) which fought alongside the Czech Legion and the White movement in the Russian Civil War.When the White government of Admiral Aleksandr Kolchak collapsed in December 1919, the Polish Legion joined the general retreat along the Trans-Siberian Railway, until it was surrounded by the Red Army east of Krasnoyarsk in early January 1920.Refusing to surrender, Rumsza led 900 officers and men on an ice march through the taiga slipping through Bolshevik forces until they reached Irkutsk.