“A skilled soldier kills your enemies, but a skilled duelist kills your allies.”
Source: World of the Five Gods series, The Curse of Chalion (2000)
Help us to complete the source, original and additional information
Lois McMaster Bujold 383
Science Fiction and fantasy author from the USA 1949
Related quotes

“If you kill your enemies, they win.”
Attributed by Gavin McInnes (AKA Miles McInnes) of Rebel Media in the satirical video "Why Miles McInnes is moving back to Canada: Trudeau's 10 Greatest Quotes!" at 5m45s number 9/10 https://www.youtube.com/watch?v=_tpW1m-8yVQ&t=5m45s", along with accompanying article as Gavin McInnes “If you kill your enemies, they win”: Justin Trudeau’s greatest quotes! https://www.therebel.media/justin_trudeau_s_greatest_quotes released the same day, then repeated by Daniel Greenfield in his article "Surrendering to ISIS is the Only Way to Defeat It", Canada Free Press (31 March 2016) https://canadafreepress.com/article/surrendering-to-isis-is-the-only-way-to-defeat-it. A Reddit thread "Any evidence that Trudeau said 'if you kill your enemies, they win'?" https://www.reddit.com/r/canada/comments/68iwe3/any_evidence_that_trudeau_said_if_you_kill_your/ questioning the veracity of the attribution was created in April 2017. No corroborating evidence was found to support the "McCinnes brothers" claims that Trudeau said this, yet many others have repeated it as fact. It is possibly a paraphrasing of Trudeau's February 2016 quote about elevating enemies.
Misattributed

Source: Cure for the Common Life: Living in Your Sweet Spot

“Your enemies can kill you, but only your friends can hurt you.”

As quoted in the Jakarta Globe http://www.jakartaglobe.beritasatu.com/features/legendary-director-garin-nugroho-shares-insights-experiences-singapore-masterclass/, Singapore International Film Festival (March 12, 2017)

Private Richard Sharpe to the Tippoo Sultan, p. 372
Sharpe (Novel Series), Sharpe's Tiger (1997)

“…So really, it's just y—" [enemy player kills him] "—oh, dammit!—you, your gun, and your friends.”
WTF Is…? series, Insurgency (standalone) (January 29, 2014)