The Prince

Machiavelli speaks only to those who would govern. The practicalities of governance do not allow the prince the luxury of moral sanction. What matters is the perception of those who would do the State harm either from inside or outside its borders. A great prince must be willing to do what others would call evil for the good of the State. That is the price those who govern must pay.
What follows is more psychology than political philosophy. Like Aristotle, navigating the norms of the day govern on the best way to choose a course of action. Though not bound morality, one can be bound by mores. As Machiavelli coldly states:
Most react negatively to the bluntness Machiavelli exhibits. But I wonder how many would be willing to sacrifice the State under which they live, including their freedom, stability and the advantages accrued, in order for their rulers to feel moral? As long as the State exists, Machiavelli’s maxims will never be irrelevant.Yet one cannot call it virtue to kill one’s citizens, betray one’s friends, to be without faith, without mercy, without religion; these modes can enable one to acquire empire, but not glory. pg.35