I notice in the manual it says:

"5.1.6.
Send Flank March
You have decided to send part of your forces on a flank march, to
catch the enemy at a disadvantage. Alternatively he might over-
run you before they arrive.
There is no scenario selection to make the enemy send a
flank march, but they may ...

Hello!

My friend and I have recently started playing P&S:C. The other day while playing an online game he noticed he was missing a few units. Most of them, not all, showed up later in a Flank March. Thing is, I picked Open Battle as the type, and confirmed it on the Multiplayer challenge screen ...