On 28 January AD 118, four days after his 42nd birthday, Hadrian celebrated the 20th anniversary of Trajan’s accession, the first since the emperor’s death at Selinus five months earlier.
Festivities took place throughout the empire as Roman citizens remembered the Optimus Princeps as a successful soldier-emperor who presided over the greatest military expansion in Roman history. However many admirers of the great Imperator must have found it difficult to accept the changes of policies of his successor, most notably the withdrawal of the Roman troops from the newly conquered provinces and the removal of high-ranking officers. These changes would soon cause anger among the generals most loyal to Trajan, four of whom might have started to conspire against the new Emperor.

Source:
- Birley, Anthony R. (1997). Hadrian. The restless emperor (p. 85)