On 27 August 1699 Steinau was promoted to the rank of the Generalfeldmarschall. With his Saxon troops he participated on behalf of Augustus II the Strong in the Great Northern War defending Livonia in the Courland campaign, and in February – November 1700 the Siege of Riga. In July 1700 he won a battle in Jungfernhof (Jumpravmuiža, Jumprava) near Riga against the young Swedish general Otto Vellingk.