Parthian Plague (Ætas ab Brian)

From Alternative History

The Parthian Plague, 919(166)-923(170), was a pandemic brought by legions returning from the conquests of Parthia. Put together with the earlier plague from Trajan's Eastern Campaign (869(116)-874(121)), nearly 3 million empire-wide were killed. The people turned to magic and sacrifice, but eventually they were found to be of little use. The Parthian Plague was also known to have proceeded into eastern Europe where it also infected numerous Ostrogoth tribes.

The military was hardest hit by the plague and to keep up garrisons, barbarian tribes with less training had to be recuited. The quality of the legions would take until the mid 11th century to fully recover, thanks in part to the reforms of Gaivs Constantinvs.