Cassius's army, although suffering from a shortage of supplies and the effects of a plague contracted in Seleucia, made it back to Roman territory safely. Lucius took the title Parthicus Maximus, and he and Marcus were hailed as "imperatores" again, earning the title 'imp. III'. Cassius's army returned to the field in 166, crossing over the Tigris into Media. Lucius took the title 'Medicus', and the emperors were again hailed as "imperatores", becoming 'imp. IV' in imperial titulature. Marcus took the Parthicus Maximus now, after another tactful delay. On 12 October of that year, Marcus proclaimed two of his sons, Annius and Commodus, as his heirs.