Notes from Wikiquote
My father taught me many things here. He taught me in this room. He taught me: keep your friends close but your enemies closer. | Niccolò Machiavelli, who is also sometimes credited, wrote on the subject in The Prince | It is easier for the prince to make friends of those men who were contented under the former government, and are therefore his enemies, than of those who, being discontented with it, were favourable to him and encouraged him to seize it. | There are also some attributions of a relatable comment to Genghis Khan | To know your Enemy, you must become your Enemy. | This is sometimes attributed to Sun Tzu in combination with the above quote, as well as alone, but it too has not been sourced to any published translation of The Art of War, though it is similar in concept to his famous statement in Ch. 3 : "It is said that if you know your enemies and know yourself, you will not be imperiled in a hundred battles..."