Statement in conversation with John Croker https://en.wikipedia.org/wiki/John_Wilson_Croker and Croker's wife (4 September 1852), as quoted in The Croker Papers: The Correspondence and Diaries of the Late Right Honourable John Wilson Croker, LL.Dm F.R.S, Secretary of the Admiralty from 1809 to 1830 (1884), edited by Louis J. Jennings, Vol.III, p. 276.
“War is a cruel business and there is brutality in it on all sides”
            Letter to Lucy Webb Hayes, whose cousin was a prisoner and died at Andersonville prison (2 July 1864) 
Diary and Letters of Rutherford Birchard Hayes (1922 - 1926) 
Context: You use the phrase “brutal Rebels.” Don’t be cheated in that way. There are enough “brutal Rebels” no doubt, but we have brutal officers and men too. I have had men brutally treated by our own officers on this raid [to Lynchburg, Va. ]. And there are plenty of humane Rebels. I have seen a good deal of it on this trip. War is a cruel business and there is brutality in it on all sides, but it is very idle to get up anxiety on account of any supposed peculiar cruelty on the part of Rebels. Keepers of prisons in Cincinnati, as well as in Danville, are hard-hearted and cruel.
        
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Rutherford B. Hayes 70
American politician, 19th President of the United States (i… 1822–1893Related quotes
                                        
                                         UFC 178 post-event press conference https://www.youtube.com/watch?v=zAAC34JzxS0 (September 2014), Ultimate Fighting Championship, Zuffa, LLC 
2010s, 2014
                                    
Source: Intuitions and Summaries of Thought (1862), Volume I, p. 82.
“War is a bloody business, a killing business.”
Source: George S. Patton's speech to the Third Army https://en.wikipedia.org/wiki/George_S._Patton%27s_speech_to_the_Third_Army
“In war, whichever side may call itself the victor, there are no winners, but all are losers.”
                                        
                                        Speech at Kettering, (3 July 1938), The Times (4 July 1938) 
Prime Minister
                                    
“Wars, conflict, it's all business. "One murder makes a villain. Millions a hero."”
                                        
                                        Numbers sanctify. 
Monsieur Verdoux (1947); Chaplin in this line is quoting an older statement of Bishop Beilby Porteus: "One murder makes a villain. Millions a hero."