[quote=@Zebanamana]
It's harsh terrain and they can't move the horses very quickly until they are in more open land. Horses can ride through dense forest and undergrowth, but they move slowly because they need to find the right footing. Eadwig was not there when Fanilly told them to dismount, and as a character he sees being mounted as more advantageous than being unmounted. He is a stubborn old man.
[/quote]

Everyone else in front of him was blatantly dismounted, it's a really thick forest, and it's sunset. Including characters he put in charge of cavalry...