GTI wrote:

I dont agree with this statement because diplomacy can break a faction or a country. For example, when I used to play Total War: Three Kingdoms, I had the faction with the highest amount of food and I was always making trading it to get a lot of money from the most dangerous faction and the others while I only provided enough food for my main enemy - the one with the highest amount of money  - to survive but drastically reducing his potential to create new armies. Meanwhile I still had a lot of food and much money from all the trades. 

上兵伐谋，其次伐交，其次伐兵，其下攻城

Therefore, the best strategy for the use of troops is to defeat the enemy's strategy, the second is to destroy the enemy's diplomacy, and the third is to attack the enemy's army, and the lowest strategy is to attack the enemy's city. Siege is the last resort.

The Art of War is more likely to say, one of the great philosophical works than the tactical manual. There's some people already talked about the importance of preparation before actually getting into the war and how you behave when you start the war, and I mean, yeah technically you can apply the theory of the Art of War into the game. I watched some of the combat videos of the Humankind and the system and the terrain parts are better than Civ series but more simple than the Total War series. However I believe it's still good enough to apply any kind of 'tactics' while you fight.

I have a printed copy of The Art of War and I don't understand some Sun Tzu statements because they are not applied in a context. But I was able to understand most part of his philosophy. 

For example, Sun Tzu's statement: "Treat your prisoners well"; Depending on the prisoner and how much he likes his faction, he is unlikely going to betray it to side with the new one. at the first opportunity, the prisoner will backstab the faction leader !

In my opinion, this (a little long) quote is the closest thing to a "general 4x strategy manual":
"
. If your enemy is secure at all points, be prepared for him.
. If he is in superior strength, evade him.
. If your opponent is temperamental, seek to irritate him.
. Pretend to be weak, that he may grow arrogant.
. If he is taking his ease, give him no rest.
. If his forces are united, separate them.
. If sovereign and subject are in accord, put division between them.
. Attack him where he is unprepared, appear where you are not expected .”
"

Thank you for the explanation ANGRYABOUTELVES!

"The essence of war is violence! Moderation in war is imbecility!" - Fisher

"Der Krieg ist eine bloße Fortsetzung der Politik mit anderen Mitteln" (war is a continuation of policy by other means) - Clausewitz

and, as mentioned earlier,

"Parabellum".

Or in other words, war is, or at least should be, performed for a purpose. Fighting for the sake of fighting is pointless. You go to war because you desire something that cannot be obtained by words alone. When you do go to war you don't pussy around. You are either fighting your enemy or you are not. If you are willing to use violence against your enemy, use ALL of it.

And if you want peace, perpare for war.

Having said all this, Fisher was... an interesting historical figure. History is probably a better place because he was not actually allowed to dictate foreign policy. However his point was that war involves the direct application of violence. Foreign policy (Clausewitz's point) can involve the threat of violence (which is also part of the Parabellum concept) but once you decide to use that violence, use it. To paraphrase from the Shlock Mercenary web comic, 'There is no such thing as overkill, there is only 'open fire' and 'I need to reload''.

So how does this relate to 4X? Going to war should be for a reason, both for players and AI. Why are you at war? What are you trying to achieve? What do you want and/or what are you trying to stop the other nation/kingdom/empire doing against you? Remember in the real world wars can be very expensive to maintain. Either you have to have a large percentage of your population called up as feudal type levy - which means they are don't at home doing things you can tax them for - or you are paying large amounts of mercenaries to do the fighting for you. Either way extended wars start costing the earth and you shouldn't be allowed to fight 1000 year wars just for the convenience of it.

Or something :D

“To know your Enemy, you must become your Enemy.” – Sun Tzu

My FAVORITE !!!

I want to become CHINA

The fact that you asked that question shows the strategem of your mind. I beilve like others have said, to apply it to all parts of the games and life, is very fundemantal. High Ground, know your terrain, let your enemy come to you, enemy of my enemy is my friend.