"Eliminate them" (4.3). By using clinical terms like "eliminate" in The Prince, instead of more straightforward and maybe disturbing words like "murder," "kill," or "massacre," Machiavelli makes killing, and war, seem like an everyday matter. He says that war crimes are "normal" and "natural" (3.1). Not only that, but war is necessary for all new rulers to maintain power. So what is warfare? It's a tool. You have to use it, so you might as well get on with it and not worry about the details. Well, except that Machiavelli is obsessed with the details. Yet another example of the mixed-up files of Niccolò Machiavelli.
Warfare is the primary duty of rulers in The Prince.
According to Machiavelli, it is impossible to wage war without "endless injustices" (3.1).