Decius may have been born around AD 201 to a senatorial family. He was governor in Moesia in the mid 230s. Decius married Herennia Cupressenia Etruscilla. Philip the Arab sent Decius to restore order along the Danube. When he arrived local troops killed Marinus, who had established himself as emperor in the area. The troops named Decius emperor and asked him to lead them in revolt against Philip the Arab. After Philip died, either in the fighting or by assassination, Decius was made emperor. Decius took on the name "Trajan" partly for its association with the area in which he had served and partly because of the respect in which Trajan was held. He implemented a building plan and, according to Christian sources, a persecution. Decius died while on campaign near Nicopolis with his son Herennius Etruscus fighting the Goths at Abrittus, late in AD 251.

Main Roman Coin Book and Other References:

RIC = Mattingly, Harold    The Roman Imperial Coinage
BMC = Coins of the Roman Empire in the British Museum
RSC = Seaby, H A    Roman Silver Coinage
RCV = Sear, David R    Roman Coins and Their Values
Cr = Crawford, Michael    The Roman Republican Coinage
SB = Sear, David R    Byzantine Coins and Their Values
S = Coins of England and the United Kingdom
WW = Wildwinds.com (reference & attribution site)