He devastated the surrounding countryside and took an enormous booty before an army of Otto I, Holy Roman Emperor forced the Greeks to retreat. In 974, Marinus allied with Manso I of Amalfi and Landulf of Conza to depose Gisulf I of Salerno. They were defeated, however, by the intervention of Pandulf Ironhead.
He ravaged the surrounding countryside and amassed a massive haul before an army of Otto I, Holy Roman Emperor compelled the Greeks to withdraw. In 974, Marinus formed an alliance with Manso I of Amalfi and Landulf of Conza to overthrow Gisulf I of Salerno. However, they were ultimately defeated by Pandulf Ironhead's intervention.