Slitherine

I've recently had an instance where a BG of routing light skirmishers went through 2 BGs of Heavy foot and disrupted both. I can't recall having seen this before. In the same game, evading LF went through MF but with no effect.

This is what Help offers:
In various circumstances, battle groups may be forced to burst through other battle groups that they cannot normally interpenetrate. This is not voluntary and can cause difficulties. Where a battle group can normally interpenetrate friends there is no penalty, otherwise:

A battle group burst through by friendly shock troops drops one cohesion level.
A battle group burst through by friendly evading troops drops one cohesion level.
A battle group burst through by friendly routing troops drops one cohesion level.

I assume "various circumstances" relates to routs and evasions but what does "normally interpenetrate mean? Why were the MF not affected but the HF were?

Can you check the skirmishers are correctly set as such and are not one of the Medium Foot mascarading as Light foot units?

This happened in the last, my Brigante , turn in a MP of 'Agricola Moves North' against pantherboy.

I have not yet had a return file so cannot look at that actual game but looking through the game vs AI, it seems that all the lights are correctly identified - assuming that scrolling through them and checking the bottom left -hand info box is sufficient.

It was the roman MF bows that routed through two other units. Agricola doesn't have any lights for the romans.

Ha, my mistake. Got my sides mixed up completely. Must be old age; that's my excuse anyway.