Ingenuus had also been charged with the military education of Caesar Cornelius Licinius Valerianus, the young son of Emperor Gallienus, but after the boy's death in 258, his position became perilous.

[3] A well-liked and admired commander,[4] Ingenuus found an opportunity to become the Roman Emperor when Valerian was captured and killed by Shapur I of the Sassanid Empire.

[1] Throwing off their allegiance to Valerian's son, the legions of Moesia proclaimed Ingenuus Roman Emperor at Sirmium in 260.

[1] Gallienus was in Germania on the Rhine frontier,[citation needed] so he acted quickly by recalling troops from Gaul and after a rapid march he met Ingenuus on the battlefield at Mursa.

[1] The troops of Ingenuus were defeated, as Gallienus' general, Aureolus, used to great effect the advantage given by the mobility of an improved cavalry component of the army, which was the remarkable military innovation wanted by the Emperor.