Nerva 's brief reign was marred by financial difficulties and his inability to assert his authority over the Roman army . A revolt by the Praetorian Guard in October 97 essentially forced him to adopt an heir . After some deliberation Nerva adopted Trajan , a young and popular general , as his successor . After barely fifteen months in office , Nerva died of natural causes on 27 January 98 . Upon his death he was succeeded and deified by Trajan .