One more snippet. There may have been some forms of signalling used to convey information which would have been confirmed by written or verbal reports.
Crauford's cavalry outposts in the Peninsula would react to observing the advance of a French force by circling before retreating. Clockwise circling would indicate advancing infantry, counterclockwise indicating cavalry (working from memory on this so apologies if I have this the wrong way round). An advance by a force of all arms would be signalled by two groups circling, one clockwise, the other anticlockwise).
HQ would observe this and as a result the main body of the Light Division would be prepared to react and heavy transport could be sent off to the rear in good time.
I suspect other armies had techniques for conveying information by visible signals. Just simply observing that the support squadron was able to move forwards would indicate no enemy within close proximity.