brother-in-law of Caligula
father-in-law of Domitian

Able & popular Roman general, who despite--or due to--his record of military & political successes was ordered by Nero to commit suicide.  Corbulo survived the assassination of his imperial brother-in-law and unpopular half-sister (41 CE) just two years after his term as consul. But it was only in 47 CE when Claudius gave him command of the army of the lower Rhine (Germania Inferior) that he began to demonstrate his abilities by restoring military discipline, pacifying the local tribes, & constructing a canal that still connects the Rhine & Meuse rivers in the Netherlands.

In 54 CE the new emperor (Nero) gave him command of two legions in Cappadocia (eastern Asia Minor) after Parthia violated a treaty with Rome by installing one of its own as king of neighboring Armenia, a nominally independent client kingdom of Rome. With his army reinforced by a legion from the Danube Corbulo invaded Armenia (58 CE), sacked its capitols, expelled the Parthian pretender & installed Rome's own candidate--Tigranes VI, a great-grandson of Herod--as king. Such success led Nero to appoint him governor of Syria when Quadratus died (60 CE).

Tigranes , however, soon violated the truce with Parthia by invading neighboring Adiabene, a former Armenian province that had become a client state of Parthia. When Parthia responded by attacking Armenia, Corbulo's replacement in command of the Cappadocian legions suffered a major defeat. Unable to win a decisive military victory for Rome, Corbulo brokered a face-saving truce (63 CE) by agreeing to withdraw troops from Armenia, remove Tigranes & allow the Parthian candidate to be king, providing he go to Rome to be installed by Nero. Desperately in need of a triumph to bolster his sagging popular support, Nero recalled Corbulo to Rome to celebrate this peace with Parthia as a major triumph. Nero's imperial propaganda turned Corbulo into a national celebrity. Four years later Corbulo obeyed the emperor he had served so well when out of jealously the latter ordered him to commit suicide. Ironically, less than a year later Nero followed suit.

References: Tacitus, Annals 13.8-9,34-41, 14.23-26, 15.1-17,24-31. 
                   Dio Cassius, Roman History 60.30, 62.19-23, 63.17.

Other resources on line:

• Gnaeus Domitius Corbulo - succinct, well-sourced article from 1911 Encyclopedia Britannica.

• Gnaeus Domitius Corbulo - Jona Lendering's extended analysis of Corbulo's life and campaigns [Livius.org].

• Gnaeus Domitius Corbulo - article in Wikipedia's web.