Concealing Infantry movements

[Felix]

I seriously doubt that Caesar took every third man from the legions deployed across his center when he reinforced his cavalry wing. Small unit cohesion would suffer severely under this condition, as he would have been mixing men of different centuries, cohorts, and even legions in his new formation. Fighting with comrades you know and trust is the sine qua non of small unit cohesion. It is far more likely he took whole cohorts or centuries and moved them intact to reinforce his cavalry. That is also my recollection of the way the battle is described.

German WWII kampfegruppen (?) were a related phenomenon, as they were generally made up of small units which were transferred intact into a new command; not men pulled out of their small units and expected to make up new ones.