Ricimer used his new position to assist his colleague Majorian in plotting against Avitus, who had not yet been recognized as Emperor of the West by Marcian, the Eastern Emperor. Ricimer and Majorian convinced the Roman Senate to authorize a military expedition against Avitus, who had established himself at the imperial capital of Ravenna. The two led an army against an imperial force commanded by the "magister militum" Remistus which they defeated; Remistus was executed at Classis in Ravenna on September 17, 456. Avitus fled to Gaul to gather support and army from his Visigothic and Gallic followers. A month later, on October 16, Avitus returned but was heavily defeated in Piacenza by Ricimer. The emperor was captured, forced to assume the bishopric of Piacenza, and finally executed. With the Western throne vacant, the new Eastern Emperor, Leo I, granted Ricimer the title of patrician and the rank of "magister militum" on February 28, 457. Leo appointed Majorian to replace Ricimer in his Italian command. Without a Western Emperor, Leo hoped to use Ricimer as his effective viceregent in the West.