When Philip, the Romanized Arabian, got selected as the Praetorian Prefect, Gordian III at that time was fairly popular ruler.

This post was highly influential, and under Gordian, one of Philips’s duties was to control the supply logistics of the military. 

As he wanted to be emperor himself, and was highly ambitious for it. So, he deliberately mismanaged the food supply of soldiers in hopes that the blame would be put on the emperor.

Well, this actually worked really well because the soldiers due to extreme hunger ultimately mutinied, and killed Gordian. Before the conspiracy of treason would be investigated, Philips achieved his plan by claiming him as the emperor, which the senate too agreed. 

A successful leader on the battlefield, that’s how Philip turned out to be.

A peace treaty was negotiated with the Persians, after which he went back to Rome. However, when the new revolts started arising along the Danube, the Trajan Decius was sent off to take care of the situation.

A totally poor judgment was this on his part, since the Decius would end up doing a great job which his soldiers promoted to the Augustus, arbitrarily.

An army was gathered and prepared to fight Decius, however, he got beaten and ultimately killed in the battle.