Werner was originally a Swabian count who was sent as captain of the German contingent of 700 infantry and cavalry by the Emperor Henry III to assist Pope Leo IX at the Battle of Civitate.
Subsequent to that great defeat, during which his Swabians were routed by Richard I of Capua, Werner conquered a swathe of Adriatic territory centred on the Pentapolis.
He henceforth appears in chronicles and charters as Dux et Marchio Guarnerius and Guarnerio Marchione.
In November 1105, Werner went to Rome with an army of Germans in support of the Antipope Sylvester IV.
At his coming, Pope Paschal II fled to the Tiber Island.