Use of the standard to issue commands?

[Caballo]

Well, its a LOT later, but it certainly happened at Manzikert when the Byzantines were beaten by the Turks in 1071.

"The final campaign against the Turks was launched in 1071, headed by the Emperor. The army’s size was regarded with awe by contemporary historians, up to the ridiculous figure of 1 million (17) according to Matthew of Edessa. In reality the army probably comprised 40,000 men , very sizable for a medieval army. Romanus followed the traditional Byzantine strategy of deception in proposing peace with the Seljuk leader Alp Arslan while marching east to retake the Armenian border fortresses which had fallen into Turkish hands. When Alp Arslan did realise the danger, he hastened to Armenia to confront Romanus. Half the Byzantine army under Joseph Tarchaniotes withdrew back to Constantinople without joining battle, leaving Romanus and the other half of the army to face the Turkish force which was reckoned at being roughly equal in size . In the battle itself the internecine weaknesses of the Byzantine state played themselves out. The mercenary Normans refused outright to fight at the moment of battle, while the mercenary Turkish Uz horsemen defected from the Byzantine army the night before the battle to join the Seljuks, thereby causing great unrest in Romanus’ army. At the critical moment of battle, when the Turks charged around to flank and surround Romanus, the Byzantine rearguard need only to have charged forward and crushed the Turks in a vice. But commanding the rearguard was Romanus’ bitter political rival, Andronicus Ducas. Almost definitely in order to help his family seize the Byzantine throne after a major defeat, Andronicus suddenly reversed the imperial standards on the battlefield to signal a retreat . The result was an utter rout of the Byzantine forces and the loss of the battle. Not through any poor performance of soldiers or commanders had Manzikert been lost, but through the hollow strength of Byzantium’s military and her politically suicidal feuding for control of the throne in Constantinople."