After Severus was murdered in 235, he was proclaimed emperor by the army, beginning the Crisis of the Third Century, a 50-year period of instability and civil war.

Maximinus advanced on Rome to put down the revolt, but was halted at Aquileia, where he was assassinated by disaffected elements of the Legio II Parthica.

[11] According to the notoriously unreliable Historia Augusta, he was born in Thrace or Moesia to a Gothic father and an Alanic mother;[12] however, the supposed parentage is a highly unlikely anachronism, as the Goths are known to have moved to Thracia from a different place of origin much later in history and their residence in the Danubian area is not otherwise attested until after Maximinus' death.

[14] On the contrary, Bernard Bachrach suggests that the Historia Augusta's use of a term not used in Maximinus time – "Gothia" – is hardly sufficient cause to dismiss its account.

Hence, Bachrach argues, the most straightforward explanation is that the author of the Historia Augusta relied on a legitimate third century source, but substituted its terminology for that current in his own day.

His background was, in any case, that of a provincial of low birth, and he was seen by the Senate as a barbarian, not even a true Roman, despite Caracalla’s edict granting citizenship to all freeborn inhabitants of the Empire.

[16] According to the Augustan History, he was a shepherd and bandit leader before joining the Imperial Roman army, causing historian Brent Shaw to comment that a man who would have been "in other circumstances a Godfather, [...] became emperor of Rome.

[20] The troops, who included the Legio XXII Primigenia, elected Maximinus, killing Alexander and his mother at Moguntiacum (modern Mainz).

[23] The first was during a campaign across the Rhine, when a group of officers, supported by influential senators, plotted to destroy a bridge across the river, in order to strand Maximinus in hostile territory.

[32] Maximinus, wintering at Sirmium, immediately assembled his army and advanced on Rome, the Pannonian legions leading the way.

[22] According to early church historian Eusebius of Caesarea, the Imperial household of Maximinus' predecessor, Alexander, had contained many Christians.

[43] According to Historia Augusta, which modern scholars however treat with extreme caution: The Romans could bear his barbarities no longer – the way in which he called up informers and incited accusers, invented false offences, killed innocent men, condemned all whoever came to trial, reduced the richest men to utter poverty and never sought money anywhere save in some other's ruin, put many generals and many men of consular rank to death for no offence, carried others about in waggons without food and drink, and kept others in confinement, in short neglected nothing which he thought might prove effectual for cruelty – and, unable to suffer these things longer, they rose against him in revolt.

[44] Ancient sources, ranging from the unreliable Historia Augusta to accounts of Herodian, speak of Maximinus as a man of significantly greater size than his contemporaries.

[50] It is very likely however that this is one of the many exaggerations in the Historia Augusta, and is immediately suspect due to its citation of "Cordus", one of several fictitious authorities the work cites.

"[52] Some historians interpret the stories on Maximinus's unusual height (as well as other information on his appearance, like excessive sweating and superhuman strength) as popular stereotyped attributes which do no more than intentionally turn him into a stylized embodiment of the barbarian bandit[53] or emphasize the admiration and aversion that the image of the soldier evoked in the civilian population.