HOMM 6 should include the following:
1. Pallisade fortification (various improvised forms)
2. Army encampment (basically a collection of a few tents, campfire and some makeshift spikes/ pallisade)
3. Ruin fortress (decayed and crumbling ruin turned into makeshift fort)
All these are fixed strategic defense points, both defendable and conquerable by all. These things, unless you own them, block mountain passess, river crossings and access paths. The attacker is at a disadvantage, the defender at an advantage. This allows you to conquer and control large areas, at the same token if you lose them, it will be hard fought to get them back again. It just adds more gameplay time to the game, increases strategic depth and options. This is how war is fought, especially with hand weapons.