Caelius was tribune of the "plebs" in 52 and curule aedile in 50. During this period he wrote a series of witty and informative letters to Cicero, who was serving as proconsul of Cilicia at the time. After much hesitation, Caelius sided with Julius Caesar against Pompey in the civil war, warning Cicero accordingly not to align his fortunes with Pompey: in 48 BC he was rewarded with the office of "praetor peregrinus" (“judge of suits involving foreigners”). However, when his proposed program of debt relief was opposed by the Senate and he was suspended from office, he joined in a rebellion against Caesar which was quickly crushed. It was during this rebellion that Caelius was killed.