Diary of an Unknown (1988)
“Your Worst Enemy Could Be Your Best Friend && Your Best Friend Your Worst Enemy”
Source: The Goblin Quest Series, Goblin Hero (2007), Chapter 7 (p. 117)
“Count me not your friend but the enemy of your enemies.”
Source: Lyonesse Trilogy (1983-1989), The Green Pearl (1985), Chapter 8, section 3 (p. 480)
“At some point in the past, this person was (arguably) your best friend.”
Chuck Klosterman IV: A Decade of Curious People and Dangerous Ideas (2006), Recognizing Your Nemesis
“You've got to take it on faith that the enemy of your enemy is your friend.”
Source: Last Sacrifice
Understanding Islam, "Morals and Ethics" http://vod.dmi.ae/media/96716/Ep_03_Morals_and_Ethics Dubai Media
“Keep your friends close, and your enemies closer.”
Machiavelli commented on the relative ease of gaining favor from friends and enemies in Chapter 20 of The Prince, quoted above. However, this particular wording comes from a line spoken by Michael Corleone in The Godfather Part II (1974), written by Mario Puzo and Francis Ford Coppola:
My father taught me many things here. He taught me in this room. He taught me: keep your friends close, but your enemies closer.
Misattributed
