I know plenty of people have complained about the AI in Civilization V openly playing to win. Since some people would rather the AI offer a narrative, but ultimately hollow, threat (for Let's Play purposes) to their civilization's rise to power. However, personally I have nothing wrong with the AI playing by the same rules and trying to also win militarily, scientifically or culturally.
After all, in Shogun 2 where is the fun in claiming the Shogunate and dominance over Japan if the resistance put forth by the others Clans is purely just to make the narrative behind my rise to power somewhat interesting. Now I'm not saying that is how the Shogun 2 AI operates, however the tension and thrill behind the narrative dissipates for me if the war for the Shogunate happens to be a farce. If the Ashikaga are just keeping the seat warm for me and no one else is able to win then it is not really a war for the Shogunate but rather a story about whether or not I can overcome all the challenges needed to reach the victory conditions. The game's premise of portraying the essence of the Sengoku Jidai would fall apart for me.
No doubt playing the campaign is still fun regardless of whether the narrative behind it is a farce or not since the gameplay is still fun and challenging. However, outside of needing to achieve the victory conditions within a certain time-frame there is no narrative reason for me to hurry, it is not like anyone could win and cut my ambitions and campaign short. There are still gameplay reasons why you might not want to take your time, but nothing that makes you think: "Oh no the Oda are close to winning the campaign I better come up with a plan to stall them quickly."
Personally I cannot say either way whether or not the AI clans in Shogun 2 are attempting to win the campaign since I can only report on my personal experiences. For all I know the AI may well be attempting to play to win and it may just, more often then not, lose momentum somewhere along the line. Since despite seeing hundreds of examples of the AI looking like it does not play to win I have once seen the AI look quite convincingly like it does play to win.
It have only experienced once, but in one special campaign the AI controlled Takeda did keep progressing towards victory without losing momentum like the AI quite often seems to do. The Takeda were on the warpath towards victory that campaign and actually managed to take Kyoto and the Shogunate. It was glorious to see the AI learn the perils of Realm Divide that day. While the Takeda would eventually be brought back to earth by the surviving clans, including me, that day they looked like they could win had they been ready to withstand the intense rigours of Realm Divide.
That campaign has to be the greatest I have ever played for the purposes of suspense and portraying the Sengoku Jidai convincingly. I've still no confirmation if the AI can actually cut short anyone's campaign by meeting the victory conditions like in Rome: Total War, but that day the Takeda were out to scare me that they could, and it was exciting. Shame it would seem to be a once in a lifetime event as I would love for it to happen with more frequency and strengthen my love for playing Shogun 2.
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I were going to comment in depth on your two campaigns Afty but I seem to have written quite the long post as it is. Your Rise of the Samurai campaign looks like it is quite interestingly poised though, and I await its conclusion.[This message has been edited by Scipii (edited 02-10-2013 @ 02:06 AM).]