He was suffect consul and in 250 was made governor of the Roman province of Moesia Superior, an appointment that showed the confidence of Emperor Decius in him.

[6] In June 251, Decius and his co-emperor and son Herennius Etruscus died in the Battle of Abrittus at the hands of the Goths they were supposed to punish for raids into the empire.

According to rumours supported by Dexippus (a contemporary Greek historian) and the thirteenth Sibylline Oracle, Decius' failure was largely owing to Gallus, who had conspired with the invaders.

In any case, when the army heard the news, the soldiers proclaimed Gallus emperor, despite Hostilianus, Decius' surviving son, ascending the imperial throne in Rome.

[13] Persian invasions were repeated in the following year, but now Uranius Antoninus (a priest originally called Sampsiceramus), a descendant of the royal house of Emesa, confronted Shapur and forced him to retreat.

Despite these dispositions, Aemilian marched onto Italy ready to fight for his claim and caught Gallus at Interamna (modern Terni) before the arrival of Valerian.

[16] Gallus’s ascension and the subsequent events underscore the delicate balance of power in third century Roman Empire where the survival of an emperor depended not only on alliances and military might but also on the ability to navigate the complexities of political legitimacy and public perception.