Machiavelli

Thoughts from The Prince:

New principalities are the ones that present problems...you always have to give offense to those over whom you acquire power when you become a new ruler, bother by imposing troops upon them, and by countless other injuries that follow as necessary consequences of the acquisition of power. Thus, you make enemies of all those to whom you have given offense in acquiring power, and in addition you cannot keep the goodwill of those who have put you in power, for you cannot satisfy their aspirations as they thought you would. At the same time you cannot use heavy-handed methods against them, for you are obliged to them. Even if you have an overwhelmingly powerful army, you will have needed the support of the locals to take control of the province.

...

But when you acquire territories in a region that has a different language, different customs, and different institutions, then you really have problems, and you need to have great good fortune and great resourcefulness if you are going to hold on to them. One of the best policies...is for the new ruler to go and live in his new territories...for if you are on the spot, you can identify difficulties as they arise, and can quickly take appropriate action. If you are at a distance, you only learn of them when they have become serious, and when it is too late to put matters right. Moreover, if you are there in person, the territory will not be plundered by your officials.

That's enough for now.

Of course, this is one of many books of wisdom of all types that contains advice that should be commonly known to all. It's depressing to think how little we've learned over the past few thousand years and how we're repeating mistakes in Iraq that learned people have known how to easily avoid since before Christ.