 During the period that began with the accession of the Emperor Nerva and ended with the death of the Emperor Commodus , the Empire continued to weaken . It was becoming difficult to recruit enough soldiers for the army , inflation was becoming an issue , and on at least one occasion , the Empire almost went bankrupt . The most significant constitutional development during this era was the steady drift towards monarchy . M. Cocceius Nerva succeeded Domitian , and although his reign was too short for any major constitutional reforms , he did reverse some of his predecessor 's abuses . He was succeeded by Trajan in 98 , who then went further than even Nerva had in restoring the image of a free republic , by , for example , allowing the senate to regain some independent legislative abilities . Hadrian succeeded Trajan as Emperor . By far , his most important constitutional alteration was his creation of a bureaucratic apparatus , which included a fixed gradation of clearly defined offices , and a corresponding order of promotion . Hadrian was succeed by Antonius Pius , who made no real changes to the constitution . Antonius Pius was succeeded by Marcus Aurelius in 161 . The most significant constitutional development that occurred during the reign of Marcus Aurelius was the revival of the republican principle of collegiality , as he made his brother , L. Aelius , his co @-@ emperor . In 169 , Aelius died , and in 176 , Marcus Aurelius made his son , L. Aurelius Commodus , his new co @-@ emperor . In 180 , Marcus Aurelius died , and Commodus became Emperor . Commodus ' tyranny revived the worst memories of the later Julian emperors , as he was more explicit than any of his predecessors in taking powers that he did not legally have , and in disregarding the constitution . He was killed in 192 . 
