An army that was often willing to support its general over its emperor, meant that if commanders could establish sole control of their army, they could usurp the imperial throne from that position. The so-called Crisis of the Third Century describes the turmoil of murder, usurpation and in-fighting that followed the murder of the Emperor Alexander Severus in 235 AD. However, Cassius Dio marks the wider imperial decline as beginning in 180 AD with the ascension of Commodus to the throne, a judgement with which Gibbon concurred, and Matyszak states that "the rot ... had become established long before" even that.