The decision made by Tiberius Julius Alexander in Alexandria was a significant turning point in the Year of the Four Emperors, a year of unrest following the death of Nero. During this tumultuous period, multiple leaders vied for control of the Roman Empire, leading to widespread civil disorder. The legions out of Alexandria were vital, as control over this strategic location meant control over the grain supply to Rome, which was crucial for political stability. By rallying his legions to swear allegiance to Vespasian, Tiberius Julius Alexander not only reinforced Vespasian's claim to the throne but also helped shape the trajectory of Roman politics during this crisis.

Tiberius, who had previously served in administrative roles within the empire, understood the gravity of the situation. His choice to support Vespasian stemmed from the realization that Vespasian's military experience and popularity among the ranks offered a more secure future for the Empire compared to his rivals, Galba and Vitellius. This military endorsement was pivotal as it marked the first major victory for Vespasian, galvanizing other legions and Republican allies to join the cause, thus paving the way for Vespasian’s eventual victory.

Ultimately, Tiberius’ actions helped facilitate a transition of power that would lead to Vespasian establishing the Flavian dynasty. This period redefined military loyalty and political allegiance within the Roman Empire, setting a precedent for future emperors in maintaining their rule through military support. Alexandria, therefore, became a critical stage for the affirmation of imperial authority, showing how military leadership could decisively influence political outcomes.