Wars Revamped
Wars in Warlords feel different. Possibly the most notable difference is that you are much more likely to experience wars which have more than 2 civs involved. It seems that the AI is now more willing to join an attack on a weaker enemy who already has a fight, particularly if said AI also gets something in return. On the other hand, the AI quite likes vassalage relationships. AIs won't become vassals of other AIs too often, but you're likely to see some inter-AI vassalage action almost every game.
This applies not only to peaceful vassalage but also to surrender. Indeed, it seems that the AI has been improved as far as early attacks go, and I have seen more cases of one AI declaring war somewhat early on its neighbour, and managing to be somewhat successful with it, too. If Feudalism is already discovered, it's likely enough for such a conflict to end in a vassalage relationship.
Vassals, of course, get involved in any wars that their masters get involved in. This leads to bigger wars breaking out, particularly if you, as the human player, decide to stir things up a bit by declaring war on someone who is either a master or a vassal. Even without that, however, there's the potential for more interesting things.
In one of my first games with the final version of Warlords, I really grew to appreciate what wars with more nations involved can do. Isabella, who remains just as nasty in Warlords as she had always been, declared war on Asoka and vassalized him not too long after that. Ramesses, for whatever reasons, decided to declare war on Spain. That created a 2v1 situation, since Asoka was obliged to join. Seeing that Ramesses was getting stretched a bit, Chinese declared war on him soon afterwards. I stayed out of the situation, yet there was a fully fledged war going out there with four civilizations involved. Okay, of course, given my past experiences with Isabella, I couldn't deny myself the pleasure of declaring war on her and hitting her exposed flank.
This is the sort of thing which you can expect to happen more often in Warlords. It will not happen every game, and it often requires that you join in to make the most out of the situation, but you should certainly expect more, uh, global crisis situations.
Thanks to my friend Yin, I made an experiment with the Warlords AI and vassalage. I took a Standard sized Pangaea map, added one more AI to it (sorry, didn't have the nerve for even more), and turned the Aggressive AI option on. It was pretty rough. Of course, Alexander just had to declare war on me early on, but other than that, it went nicely. Post-Feudalism, I saw interesting relationships develop. Saladin turned out to be the big one, and he vassalized Germany peacefully. His aggression boosted by the respective game option, Saladin proceeded to declare war on Louis XIV, who was sitting back in relative peace, and so France also became Arabia's vassal through capitulation.
As you may guess, this actually put Saladin close enough to a Domination victory. No, I haven't seen the AI reach domination yet, but with half of vassal's land and population counting towards the master's domination threshold, it's certainly possible for the AI to at least come rather close. In this case, it was evident that AI still lacks the high-level goal of achieving Domination as one of its strategies, because Saladin did not attempt to fight further wars to hit the required threshold, but I think Domination can now happen.
If you want to see the Warlords AI in some military action, and check out how vassalage changes the dynamics, then you should start a game with a similar setup. Pangaea or possibly Highlands, Standard or larger map with at least as many civs as are offered for it, and Aggressive AI on. I can't promise that you will like that particular game, but it certainly will give you a very nice overview.
Vassalage remains at least as interesting in the late game. You may run into a situation where there are only two major powers remaining, each of them having vassals. If so, it can break into some true world wars. I have fought a modern war in Warlords, in which everyone was involved – which, at the time, was me and four AIs, two of which were vassals, one was the master of both those, and the fourth was independent.
While modern world wars can be fun, I have to mention a weaker point that has, sadly, not been improved on in Warlords. I am talking about the AI and air units. The AI use of air units is fine – it will, if it has a sufficient air force, destroy numerous tile improvements, strike at incoming units, etc. The AI doesn't know, however, about a blitzkrieg strategy that humans can, and often will, use. This means building a truly massive air force, which bombards the enemy cities and their defenders with such power that the incoming land forces have few problems taking over an entire civ.
The AI will not execute any similar assaults, it will still rely, in modern wars, on large numbers of land units. Not that this is a problem, but a blitzkrieg with a massive air force simply is much more powerful. Of course, this leaves the AI pretty unable to defend itself against such attacks. It does build a defensive air force of Fighters, but nowhere near enough to stop or even significantly damage a squadron of 25 or more Bombers. It's not a new Warlords issue, it's just something that has not been improved upon.
Speaking of fighting wars, I really need to mention the Trebuchet, a new Medieval toy that has been given to us. Trebuchets are strength 4 units, however, with a 100% attack bonus vs. cities. It means that, in the era of Longbowmen, Trebuchets are able to not only bombard defences, but actually kill some defenders. This is a maybe minor addition, but one that I really like. It fills the huge time gap between Catapults and Cannons, and I've always felt weird when, even in the Medieval age, attacking cities directly with siege units was equal to suiciding those units. Not anymore, luckily.