The attacks on the Roman Empire are…
256 CE to 267 CE
The attacks on the Roman Empire are finally coming from within by 258, when the Empire breaks up into three separate competing states.
Since Rome is unable to protect the eastern provinces against the Sassanids, then-governor Septimius Odaenathus of Palmyra decides to use the substantial legions he has at his disposal—among them the famed Legio XII Fulminata—to defend his provinces, rather than intervene in the struggles for Rome.