The Eastern Roman Empire made multiple attempts to try to bail out its waning Western twin in the 5th century. Perhaps the most famous was towards the very end. In 467, the Eastern Emperor Marcian had a highly capable general of noble blood named Anthemius and a waning Western Empire under the rule of the Germanic general Ricimer, who had risen to power in partnership with the Emperor Majorian and had just continued to rule the West by himself after Majorian's death. Marcian imposed Anthemius on Ricimer as the new Western Emperor, getting rid of an ambitious potential usurper and attempting to breathe life into the Western Empire at the same time. The Western and Eastern Empires launched a major offensive in 468 to try to reclaim North Africa from the Vandals, but, in the disastrous Battle of Cape Bon, the Vandals launched a fireship attack that utterly destroyed the Roman troop transports, a massive defeat and setback that left the East uninterested in Western affairs for another two thirds of a century and which indicated to all the peoples of the West that the Western Empire's military force was well and truly spent and that no one would stop the Visigoths, Franks, Burgundians, etc. from dividing up what was left of the Western Roman Empire amongst themselves.

Peter Heather's The Fall of the Roman Empire talks in great detail about other Eastern Roman interventions on the West's behalf, but spends a great deal of time on this particular intervention as the de facto end of any hope for the Western Empire's survival. Ricimer promptly killed Anthemius and returned back to ruling through puppet emperors.