I haven't played it for months and months, but my last two games were on the hardest difficulty setting, starting in the North, and whilst it was a challenge, I learned to adjust and to do without multiple trade routes early / mid game. One of the advantages to starting in the North, (there are actually quite a few), is that it is easy to hold the two nearest Northern trade routes without having to invest in a huge navy, and you don't end up fighting over those trade hubs as much as you do with those located in the South. The Southern trade routes seem to be more contested, if for no other reason than their closer proximity to other factions. The Southern trade routes also had more semi-surprise attacks launched on them in the various games that I played, whereas I had much more advance warning of a hostile navy when I played in the North, as my long coastline provided me with a visual trip wire alert that hostile forces were on the way. Combine that advanced notice with the response flexibility that garrisoning naval units in front line ports gave me, resulted in my almost permanently controlling the Northern trade hubs almost the entire time, in both of my last two games.
The only other things that I can remember about my last two games was the geography problem in the middle of the map, as your front line starts out very controlled with just two other factions in contact, but then suddenly expands out to touch upon multiple new factions the instant you make a serious push south. This meant I had to keep insane numbers of troops on my front line, and that because of economic pressure I was only able to garrison my Northern towns with a token defence force. In fact none of my Northern towns were viably held by their own garrison troops, and I was instead reliant upon employing a mobile Northern field army that I would move to reinforce / retake any endangered location. This meant losing the odd Northern city from time to time, as the enemy were landing armies behind my front lines from the sea, and my response army could on occasion, be to distant and slow to respond in time to save some locations.
The game is actually quite well balanced economically in that respect, because the most practical real world answer to defending any large geographical territory is to garrison the border regions with a lightly armed trip wire, and to amass your actual response forces well behind that trip wire, so that you can then apply your maximum firepower at any point of contact. Hadrian's Wall and the Great Wall of China were both lightly garrisoned tripwires, with the actual response force located well behind that front line. The French when they created the Maginot line, learned to their cost, that diluting your forces along your entire border, and trying to hold all of that border at once, is never a good idea. It's deeply ironic that Napoleon who was one of the big believers in the trip wire approach, and of amassing all of your forces at point of contact, was of course French, but somehow or other the French managed to forget everything that he had taught them, and instead built one of the world's largest follies.
I kind of lost interest in the game because of two reasons. Firstly the diplomatic issues. On the hardest difficulty setting alliances were nearly always useless, and the inevitable way that other factions always responded to you became just to predictable and tiresome. Secondly, I also grew tired of the sheer number of the very long battles and sieges, because on the hardest difficulty setting you can't afford to auto-resolve them, and therefore you had to fight every single battle yourself until late into the end game, and eventually that repetition just became so very, very tiresome.
The problem with battles and/or siege warfare becoming a pain because of an unfair auto-resolve button, plus just to many battles / sieges that you as the player have to fight yourself, isn't unique to the TW series. Having just completed a mod for Mount and Blade that took me weeks of time and involved far to many battles and sieges, I am now convinced that this entire area of the genre needs a major rethink.
I don't want the industry to invent a fairer auto-resolve button, as it's much more fun to fight and manage the battles and sieges yourself, but I just want fewer of them, and for them to mean more. Smashing an army to bits in the real world was nearly always game over. The conquering army moved in to conquer or loot and pillage the contested territory, and that was it. The enemy didn't respawn an army a few weeks or months later, or magic one into existence, and even when the enemy had more than one army in the field at any given time, they weren't in a geographical or logistical position to instantly fight another battle for that lost territory.
It depends which period of history you look at, because sometimes a single battle was decisive, and sometimes it was a series of battles, but what it wasn't, was the RTS equivalent of MMO grind. Yes, sometimes there is an element of attrition in real wars, when they are fought for a long period of time, but not to the extremes that some RTS games take them.
Until we do evolve this element of gameplay, perhaps playing on a lower difficulty setting and pressing an auto resolve button that won't penalise you to much, is the answer to battle / siege warfare fatigue, when it comes to those non-crucial battles. The problem is that on the hardest setting, all battles are crucial until well into the late game.
I wonder if there is some way to make a campaign that just involves key battles, but each of those battles is incredibly memorable? That would require more direction from the developer when it comes to generating the type of random battles we see in TW and M&B, but if the battle was epic and decisive enough, I would prefer to fight one battle per territory, rather than a dozen in a row contesting that same territory. Perhaps something along the lines of a game of Risk, whereby the world is divided up into key regions, but the military resources / forces within reach of that region are then limited. Quite a few RTS games tried this approach a few years back, but unfortunately they didn't have much longevity, because they lacked the open world / randomness of a TW or M&B game.The battles were to scripted, the tactical battle maps were to repetitive. the games themselves to linear, etc, but there has to be a way of evolving the gameplay so that you don't have to fight every single one of the 500+ battles / sieges that make up most campaigns, if you want to play these game on a more challenging difficulty setting.
Shogun 2 is certainly a great game and very challenging, and I will go back and play it again one day, but I will hit that same fatigue point when I do.
Regards - Mr P