Final answer:
The emperor discussed is Nerva, who adopted Trajan as his successor after Domitian's assassination. This marked the beginning of the adoptive emperors era, highlighting a merit-based approach to succession during a time of Roman prosperity and stability.
Step-by-step explanation:
The emperor in question, who succeeded Domitian and was forced to adopt the general Trajan as his successor, is Nerva. Nerva reigned after the assassination of Domitian and is noted for having financial difficulties and a tumultuous relationship with the military. His reign was marked by the adoption of Trajan, beginning the period of the adopted emperors, a time considered to be the height of the Roman Empire's prosperity and stability.
Trajan's adoption was significant because it represented a shift towards merit-based succession over hereditary claims to the throne. Nerva's adoption of Trajan due to not having his own children, coupled with the latter's non-Italian background, signified a more inclusive and meritocratic approach to leadership selection within the Roman Empire.
The fact that Nerva had to adopt Trajan due to pressures from the Praetorian Guard also highlights the powerful influence the military had over Roman politics, even though the stability of the Empire during this time was generally maintained. Trajan, later known for his great military successes and good governance, would solidify the practice of adopting emperors as a means to secure capable leadership for Rome.