@wizardsonly @frontconsole : warcrimes are more if a modern concept, and do not necessarily apply on alternate worlds. Also, this does not meet Perfidy, since it is more for things like attacking under a flag of truce, but has an exemption for ruses of war meant to get the enemy to act reckless which this falls under.
@Bidorchar : a large army through a dense forest makes little sense, they tended to follow trade routes, and open plains. If there is an established road it can make more sense as a flanking maneuver, but otherwise you get slowed down to much clearing a path. Plus he will nornally lose soldiers fighting along the way, and it lengthens critical supply lines. Weakening him in the final engagement.