At some uncertain date, Pliny was transferred to the command of Germania Superior under Publius Pomponius Secundus with a promotion to military tribune, which was a staff position, with duties assigned by the district commander. Pomponius was a half-brother of Corbulo. They had the same mother, Vistilia, a powerful matron of the Roman upper classes, who had seven children by six husbands, some of whom had imperial connections, including a future empress. Pliny's assignments are not clear, but he must have participated in the campaign against the Chatti of AD 50, at age 27, in his fourth year of service. Associated with the commander in the "praetorium", he became a familiar and close friend of Pomponius, who also was a man of letters.