His father's service to Rome, on a notoriously difficult frontier, was honoured with the gift of Roman citizenship for him and his family. His son Lusius later joined the Roman army and served as an auxiliary officer in the Roman cavalry. For outstanding service, emperor Domitian rewarded him with equestrian rank but later had him dismissed from service for insubordination.
Quietus's fortunes were revived once again when a new emperor, Trajan, came to power. Quietus was brought back into the army and served as one of the emperor's auxiliary cavalry commanders during the Dacian Wars (his bareheaded Berber cavalry can be seen on Trajan's Column in Rome). After the successful conquest of Dacia, Quietus was elevated to the position of senator. He next served with the emperor during his campaign in Parthia during which he led a brilliant rearguard action, which allowed the tactical withdrawal of troops and saved them from destruction. This action brought Quietus acclaim and ensured he was well known to the army.
During the emperor's Parthian campaign in 115–116, Quietus sacked the cities of Nisibis and Edessa. When the inhabitants of Babylonia revolted, they were suppressed by Quietus, who was rewarded by being appointed governor of Judaea.
Major revolts by diasporic Jews in Cyrene (Cyrenaica), Cyprus, Mesopotamia, and Egypt resulted in the ransacking of towns and the slaughter of Roman citizens and others by the Jewish rebels, a conflict now known as the Kitos War, after a simplified version of Quietus's name. Quietus took the city of Lydda and methodically set about defeating the rebellions.