I was just fighting a war with another faction. My Sovereign is invading on his own. The enemy has hordes of spearmen that they're sending at me.
The first group was 3 spearmen, as was the second. The next turn I start moving towards their capital and I run into solitary spearmen units, except that the AI has four such units standing in the same tile. Instead of forming an army of four, which may actually damage my Sovereign, they're all alone, not grouped with each other, despite the fact that they're in the same square.
I could see if it was behavior bringing spearmen in from different directions to eventually form a group, except they were already in the same square, and that square was within move/attack range of my invading force.
Just thought I'd point it out, for whatever it's worth.
Edit: Unless this was some sort of clever delaying tactic by the enemy to give their Sovereign time to heal and defend the capital. Then that's pretty cool.