Treb rose through the ranks in the army and received a high enough stature that when Trajan Decius died in battle the army chose him to be the next emperor. His popularity with the army and public waned inexorably ever more for the rest of his reign. His first mistake, and not one which he could have easily done much about, was to settle the same war that killed Decius by buying off the enemy. For right or wrong this was viewed as an act of cowardice bordering on treason. Then came a plague that decimated the population and even claimed Hostilian who was co-Augustus with Gallus. As both disease and the withering attacks of the barbarians eroded support for the emperor he had to face yet another blow. Aemilian rose to challenge for the purple following a series of successful battles with the barbarians that gave him and his army the confidence to attempt to overthrow the troubled ruler. Gallus went through the motions and approached to confront Aemilian in battle but his commanders had had enough and killed him along with his son Volusian just before the engagement.
RIC 30, Cohen 13 AE Antoninianus Obv: IMPCAECVIBTREBGALLVSAVG - Radiate bust right, draped and cuirassed.
Rev: AETERNITASAVGG - Aeternitas standing left, holding phoenix on a globe and raising skirt.
RIC 125v Sestertius Obv: IMPCAESCVIBIVSTREBONIANVSGALLVSAVG. Bust laureate, draped, cuirassed, right.
Rev: VICTORIAAVGG; Victory standing left holding wreath and palm.
S GIC 4307 AE28 (Viminacium) Obv: IMPCVIBIOTREBONGALLOAVG; bust right.
Rev: PMSCOLVIM; Moesia standing between bull and lion.