A squad of up to 5 units can be set to “Guard Commander” in the army management screen. They will not count as a squad for the purposes of how many squads a commander can lead. These units will always start around their commander, and stay near the commander in a normal battlefield.
New to Dominions 6, units will fire their ranged weapons while guarding, but only around a range of 10, even if they could fire further.
During an assassination, they have a base 50% chance of being present to fight back against the assassin. They will move to attack, rather than stick next to their commander in these battles.