As we all know once you defeat an enemy's main army the rest tends to be a bit easy to finish off. 

Also not being able to defend your lands better is annoying, they tend to bypass your fortresses and go around destroying your resources or attacking less defended towns...often with single heroes on horseback.

There is no way to really secure your borders short of tossing out a bunch or curgen's volcanoes, which is kinda cheesy.

So how about you add wall tiles into the game that have to be attached to a fortress?  You can give fortress higher defensive bonuses and make it require a 2 to 1 or 3 to 1 army power to be able to defeat fortresses.

So if you cant defeat the fortress you have to attack the walls.  (Each tile of wall has to be built separately on the global map)

Each wall tile you attack starts a tactical battle and if you win you break that section of wall, which allows you to travel through that hole on the global map, allowing your army to ravage their country side.

Each wall tile would have a default army and each wall tile could be upgraded to have a stronger default army and stronger walls.

The tactical battle would have an actual wall in them, you on one side, enemy on the other, and in order to get to them you have to attack and destroy sections of the wall.

You can not fire projectile spells or arrows over the wall, and it would block AoE attacks (Dragon fire can destroy it but not pass through it).  This would give the defenders a couple of free rounds while you attempt to smash down the wall (They have health bars).  Also if you only knock down a single section you would be running your army through a bottle neck allowing them to swarm you on the other side, or you could knock down several sections to allow you a better advantage but it would take longer of course.

Now this opens the door for siege equipment!

You could have 3 types of siege weapons, one designed to damage walls, one for shooting over walls and damaging troops behind, and one for damaging other siege equipment over the walls.

Think battering ram, arrow carts, and balistas.

So now you can take your normal army and a siege equipment army to a wall, switch your units around in a wall siege army, break down the wall and then switch them back to your normal army, and go rampaging around their country side.

Also again you can upgrade the walls to make them stronger, to have more/better defenders and even have turrets on sections of the walls themselves (In tactical combat) that can only be destroyed by destroying that section of wall they are on top of...I can picture some cool magical orb thing on top of a section of wall that is invulnerable and shoots lightning bolts at your army, and you have to topple the wall section it is on in order to stop it.

Again all this is talking about during tactical battles against walls, not global.

Of course this also could open a whole new set of tactical spells.  You could set your walls a blaze with an enchantment spell during tactical combat to cause attackers to take damage, however it wouldnt hurt siege units like a battering ram attacking the wall.  Or you could use earth magic to strengthen or heal the walls, water magic to freeze them giving a small bit of ice damage and having a chance to freeze the attacker (Initiative loss and possible loss of turn)

Possibilities are exciting.

But as it is, you basically defeat the main army, destroy and salt the country side and move along, and you have no way to really bottleneck or secure any kind of border.

No more dealing with small annoying units swarming and destroying your resources, now they have to be strong enough get past your walls at least.

Also this stops the player from just running a bunch of single militias through the enemy kingdoms constantly destroying their resources.

Thoughts?