Why did Julian’s troops proclaim him Augustus in Paris in 360?

In 360, while Julian was wintering in Paris, his troops proclaimed him Augustus in response to a demand from the emperor Constantius II for a number of his best soldiers.1

Although these troops were ostensibly requested for service in the East, the demand was widely perceived as a maneuver to weaken Julian’s military strength and influence in Gaul, where he had established himself as a successful and popular commander. Fearing the consequences of this reduction in force and the underlying jealousy of Constantius, Julian’s army hailed him as emperor to ensure his continued leadership and their own security.12