Pompeius placed much emphasis on his fleets to prevent Caesar from crossing from Italy. One fleet, that from Rhodes, was jointly commanded by Marcellus in association with Gaius Coponius. Other than this, nothing is known of Marcellus' involvement in the Civil War. The command of the Rhodian fleet at Dyrrachium was later mentioned as being under the command of Quintus Coponius and was wrecked in a storm. It is speculated that Marcellus was a casualty of the war – at least, he was not alive a few years later when Cicero was writing or delivering his "Philippics" (March 43 BC). Marcellus is not mentioned further.