The Prince by Niccolo Machiavelli Chapter 3 Page 4

It remains to note the causes of the second, and to point out the remedies which the French King had, or which might have been used by another in like circumstances to maintain his conquest more successfully than he did.

I say, then, that those States which upon their acquisition are joined on to the ancient dominions of the Prince who acquires them, are either of the same Province and tongue as the people of these dominions, or they are not. When they are, there is a great ease in retaining them, especially when they have not been accustomed to live in freedom. To hold them securely it is enough to have rooted out the line of the reigning Prince; because if in other respects the old condition of things be continued, and there be no discordance in their customs, men live peaceably with one another, as we see to have been