It used to be that units suddenly appearing gave a significant morale shock to the enemy.
I remember a battle in Shogun where all but my general were hidden & then when the enemy got close enough, almost my entire army appeared at the same time causing a chain route without even having any combat.
On other occasions I had the reverse, with my own guys getting routed by sudden appearance of the enemy.
While not routing them, I had a vastly outnumbered defender fight off the Mongol horde in MTW with the aid of morale hit from suddenly appearing army.
Haven't noticed much effect in Rome though (albeit, I play mods RTR & EB which increase morale significantly).
Bookmarks