Clovis...unless you are an NPC and lost it to rebellion. In which case, we'll give it to you 10 straight times. Your theory wouldn't be bad if the rest of the game worked that way, but it doesn't. Also, again, if I'm fighting the Aserai (because my idiot lords can't win without me) and Sturgia declares war on us, I can't reach Sibir in time to defend it (No, some other lord in my faction owns it, but this is the example). It wouldn't matter if it had 200 defenders or 600 it would be the first place they would attack because they have strong armies at the start of war and they want the towns.
Yesterday our faction held Lycaron (not me personally). We were fighting Vlandia, who had declared war against us even though they had nothing bordering us. They kept besieging Diathma...sometimes taking it and losing it again, sometimes stopped before taking it. We had 3 armies in the area, which is not far from Lycaron. The Northern Empire declared war on us and besieged Lycaron. 2 of the 3 armies ignored the siege and went to towns farther away, presumably to restock troops or something (which is better done by breaking up the army). The 3rd and largest started heading there but because it was so slow Lycaron fell before they got there. They paused briefly considering what to do next, then decided to besiege Lycaron. They went about 2 village lengths, then stopped and headed for a town, presumably out of food. The other 2 continued to ignore the situation. So basically, I have 3 lords hogging armies doing nothing so I can't even form an army to take back Lycaron.