 On May 1 , 305 , in separate ceremonies in Milan and Nicomedia , Diocletian and Maximian retired simultaneously . The succession did not go entirely to Maximian 's liking : perhaps because of Galerius ' influence , Severus and Maximinus were appointed Caesar , thus excluding Maxentius . Both the newly appointed Caesars had had long military careers and were close to Galerius : Maximinus was his nephew and Severus a former army comrade . Maximian quickly soured to the new tetrarchy , which saw Galerius assume the dominant position Diocletian once held . Although Maximian led the ceremony that proclaimed Severus as Caesar , within two years he was sufficiently dissatisfied to support his son 's rebellion against the new regime . Diocletian retired to the expansive palace he had built in his homeland , Dalmatia near Salona on the Adriatic . Maximian retired to villas in Campania or Lucania , where he lived a life of ease and luxury . Although far from the political centers of the Empire , Diocletian and Maximian remained close enough to stay in regular contact . 
