Source: What is to be Done? (1902), Chapter Three, Section E, Essential Works of Lenin (1966)
“Undue enmity with enemies does not serve the interests of the system. Enemies must be dealt with wisely and prudently.”
             Remarks on Mahmoud Ahmadinejad  http://www.washingtontimes.com/news/2007/mar/15/20070315-111357-5226r/?page=all March 2007. 
2007
        
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Yousef Saanei 4
Iranian grand ayatollah 1937Related quotes
“He who is prudent and lies in wait for an enemy who is not, will be victorious.”
Source: The Art of War, Chapter III · Strategic Attack
Homilies on the Statues http://www.ccel.org/ccel/schaff/npnf109/Page_476.html, Homily XX
1950s, Loving Your Enemies (Christmas 1957)
“.. I served Beauty by drawing her enemies.”
                                        
                                        Quote of Paul Klee, from 'Diaries I', 1901; as quoted in 'Klee & Kandinsky', 2015 exhibition text, Lenbachhaus und Kunstbau Munich, 2015-2016  https://www.zpk.org/en/exhibitions/review_0/2015/klee-kandinsky-969.html 
on his caricatures and his satirical drawings Klee made then 
1895 - 1902
                                    
“Nothing is as dangerous as an ignorant friend; a wise enemy is to be preferred.”
                                        
                                        Rien n'est si dangereux qu'un ignorant ami;
Mieux vaudrait un sage ennemi. 
Book VIII (1678-1679), fable 10. 
Fables (1668–1679) 
Variant: Nothing is more dangerous than a friend without discretion; even a prudent enemy is preferable.
                                    
2005 February 17 - In a debate with DNC Chairman Howard Dean at Pacific University