Another: Constantius I

Here is my other CONSTANTIUS I, 293-305 AD Pre-reform Ant, Cyzicus
RIC 19a
O: FL VAL CONSTANTIUS NOB CAES
Rx: CONDOERDIA MILITUM, KB in field



Notes and Quotes from:
Constantine,
Unconquerered Emperor, Christian Victor, By Paul Stephenson

Diocletian's establishment of a Dyarchy, the rule of two emperors was clearly an ad hoc measure

"... within a few years of his elevation Maximian (Maximianus) had become a liability, no longer able to lead his army effectively, having failed perhaps twice to defeat Carausius... Diocletian himself struck against the northern barbarians in 288 and 289. In 290 his attention was required on the eastern frontier... This was not situation he had anticipated..."

"Maximian, who could not now have been saved if his army desired his removal. A natural successor, Constantius, was poised to take over. But Maximian and Constantine were linked by marriage... Diocletian anticipated either that Constantius or Maximian would conspire against him..."

Page 90
A summit was called in Milan in the winter of 290-1.

"A deal was struck that Constantius was to be appointed Caesar, Junior emperor, and would remain subordinate to Maximian... Diocletian would also appoint a Caesar, and his choice was his own Praetorian Prefect, Galerius...elevations did not take place until 293...the reason for the delay of almost 2 years is unknown."

"Constantius, although the senior of the two Caesars, was formally adopted into the junior Herculian (Hercules) line." Under Maximian.