The Prince
Conquest by fortune, meaning by someone else's virtue (Chapter 7)

According to Machiavelli, when a prince comes to power through luck or the blessings of powerful figures within the regime, he typically has an easy time gaining power but a hard time keeping it thereafter, because his power is dependent on his benefactors' goodwill. He does not command the loyalty of the armies and officials that maintain his authority, and these can be withdrawn from him at a whim. Having risen the easy way, it is not even certain such a prince has the skill and strength to stand on his own feet.

This is not necessarily true in every case. Machiavelli cites Cesare Borgia as an example of a lucky prince who escaped this pattern. Through cunning political maneuvers, he managed to secure his power base. Cesare was made commander of the papal armies by his father, Pope Alexander VI, but was also heavily dependent on mercenary armies loyal to the Orsini brothers and the support of the French king. Borgia won over the allegiance of the Orsini brothers' followers with better pay and prestigious government posts. To pacify the Romagna, he sent in his henchman, Remirro de Orco, to commit acts of violence. When Remirro started to become hated for his actions, Borgia responded by ordering him to be "cut in two" to show the people that the cruelty was not from him, although it was. When some of his mercenary captains started to plot against him, he had them captured and executed. When it looked as though the king of France would abandon him, Borgia sought new alliances.

Finally, Machiavelli makes a point that bringing new benefits to a conquered people will not be enough to cancel the memory of old injuries, an idea Allan Gilbert said can be found in Tacitus and Seneca the Younger.
detectable_content:postscript, keywords:frequency, punctuation:no_comma