Although actually, I don't think I'd have arranged my citadel that way in the first place. It's too obvious that if the outer wall does fall, you're then trapped and surrounded with no possible escape.

I'd have pre-built a cunning network of hidden tunnels underneath allowing me to flee all the way to Outer Magnolia while the Enemy still thinks I am cowering inside.

You're trapped as soon as the seige arrives, never mind when the outer wall falls...

I was already thinking the first paragraph that there was a problem with the weaponry between the two walls. The question seems to be based on the assumption that you didn't think of that until too late, though, despite having a decade to mull it over.

Indeed. Last time round, most respondents calmly accepted the premise that they hadn't realised the tactical error until it was too late, and then had to find some sort of desperation measure or other; I did get a couple of responses of the form "you should have done something or other different before even getting this far", but they were greatly in the minority.

Failing to spot the tactical error for ten years admittedly makes a lot more sense in the real situation than it does in the metaphor. No metaphor's perfect.

Perhaps because in the metaphor, everything’s been pared down to a bare minimum, whereas in the original it’s all messy, real-life, and infused with a different perspective.

If a metaphor was perfect, it would be an isomorphism.