A causeway through the marsh

In the move and move and counter-move sequence prior to the Battle of Philippi, Antonius put a causeway through the large marsh to the right of the Caesarean army. This would enable his forces to outflank those of Cassius opposite him, and also incidentally threaten to cut the conspirators off from the sea.

These are Renedra stone wall pieces painted brown and stuck onto some Big Red Bat bases. My kids say they look like chocolate rice crispies cakes.

How they look after a bit of highlighting. Rice crispies with more sugar...

Add some cheap brown gunk courtesy of Wilko, and there you have it: a bed of stones with packed earth to move legionaries through a swamp.