We should have attacked the top-left together right away. Would have saved two hours.
This.
Also, you spent pretty much all the time sieging them... in that time you could have expanded on the whole map and blatantly steamroll them with superior numbers. Well, actually *maybe* you could have outnumbered them through expansion... (more on this lower in this same post).
But you had not enough food for the army you trained, thus you couldn't wait, while they had plenty of food... time was their ally.
Maybe they would even have won if they counter-attacked after one of your failed attacks...
Yet, it is true that KaM encourages turtling.
Do you know how did they solve this problem in, for example, StarCraft?
They lessened the resources near starting sites and made them more spread out through the map.
This way, while a turtling player has superior defences, when turtling he has to give up most of the resource control. This means that he will eventually be overrun by enemy troops, unless he manages to wear them down up to the point that every resource in the map is used up and the only army left is the one he defended himself with.
And in KaM? Let's see... first of all, what are the resources in KaM?
-Stone
-Trees
-Fish
-Iron
-Coal
-Gold
-Free space
-Fertile ground
You get them all near your starting position, and you get plenty of them. To the point you don't actually want nor need to build another storehouse, ever.
You have no actual reason to expand for the simple reason that everything you need is near you, and it is behind an easily defendable chocke point.
In addition, if I'm not wrong in Cursed Ravine there even are no resources bar the ones near each starting position!
No reason at all to contest map control!
Even if you expanded all over the map, the advantage you'd get would be actually very little (also because it'd be nullified by the fact that you'd need more serfs for both building and managing the extended delivery requests).
The Market both makes things better and worse; worse because a turtling player can use it to buy whatever he is running out of, and better because an expanding player has more wares to trade for the resources he needs.
These are just my two cents on this matter.
I'm attaching an example map to explain what I mean... in this very ugly and simple map, important resources are placed between players and in an exposed position.
You can turtle, but if you do then you are cutting yourself out of Iron, Coal and Gold supplies.
Of course playing this map would result in a tower rush to control those resources, but this map is not intended to be actually played anyway... its purpose is just to illustrate what I mean when I write "there is no point in expanding beyond your town's nearest defendable borders".