Sieges and Blockades

One of the iconic scenes in fantasy literature (and medieval battle) is the siege of a castle.  In history (possibly less so in literature), a siege involved a blockade, with the intention of starving out those within the stronghold.

Representing this in an RPG is tricky.  It seems that most RPGs don't really touch it, even those which feature some measure of large scale battles.  Birthright did have the concept, although it involved tracking where units were on the map, and recording how long they remained in a zone with a fortification.  This method involves a little more book keeping than I was hoping for, as well as not fitting the season based structure of WotA.

It's fine to ignore the concept of blockade, and just focus on battles.  This would presume that any structures attacked must be taken during the same session, or the attack is thwarted.

I see two different scales in terms of warfare, a strategic zoomed out view and a tactical zoomed in view.  In the first, units wouldn't move much, as zones on the map might represent large distances.  When groups of units met, they would do battle according to some sort of rules (missile first, etc, etc).  This is a little like Birthright did it.

The second view is more Diaspora, where the zones on the map are smaller (yards, not miles), and time scales are shorter, representing a battle.

I prefer the second zoomed in view for fighting out battles, but the zoomed out view has the advantage that it provides a better framework for a logistics game - where you spend resources to starve out another faction. So, what would be a good way to allow for that aspect in the zoomed in view?

One possibility: if all the defenders are in a strongpoint of some sort, capable of providing defense, the attackers may use a special "siege" action, which effectively zooms out the time scale, costing both sides resources.  This could be done until one side cracks?

It's a little fiddly, but it may work to capture the idea without having lots of extra information to track.

Coming up with a rule that captures when that situation can occur might be tricky.  For instance, one unit could be on the map, but not really engaging the opponent?  It could be a "all defending units are outside the strongpoing, or unable to affect the attacking units" sort of rule.  That would give the defender some motivation to harry the attackers.  Otherwise, they are effectively giving up.

Then, when the scale zooms out to involve siege, it is assumed that much larger units of time pass by (weeks or months), as the people holed up whether the storm.  Eventually, one side or the other will crack, either the attackers assaulting the strongpoint, or the defenders exiting.