“We shall never go wrong if we do what is opposed to the interests of our enemy.”

1920s
Source: Nationalsozialismus oder Bolschewismus? (National Socialism or Bolshevism), open letter to “My Friends on the Left,” Nationalsozialistische Briefe (National Socialist Letters), (Oct. 15, 1925); Joseph Gobbles, Quoted in The Devil’s Disciples, Anthony Read, W. W. Norton & Company, 2005, p. 142

1950s, Loving Your Enemies (Christmas 1957)
Context: Jesus is eternally right. History is replete with the bleached bones of nations that refused to listen to him. May we in the twentieth century hear and follow his words-before it is too late. May we solemnly realize that we shall never be true sons of our heavenly Father until we love our enemies and pray for those who persecute us.

Los Angeles Almanac http://www.laalmanac.com/history/hi05s.htm
Mexican-American War

As quoted in Historic Ship Exhibits in the United States (1969), by United States Naval History Division, United States Navy, p. 24

"Saudi Arabia wasn’t always this repressive. Now it’s unbearable." in The Washington Post (18 September 2017)

Speech http://hansard.millbanksystems.com/commons/1848/mar/01/treaty-of-adrianople-charges-against to the House of Commons (1 March 1848).
1840s
Context: I hold with respect to alliances, that England is a Power sufficiently strong, sufficiently powerful, to steer her own course, and not to tie herself as an unnecessary appendage to the policy of any other Government. I hold that the real policy of England—apart from questions which involve her own particular interests, political or commercial—is to be the champion of justice and right; pursuing that course with moderation and prudence, not becoming the Quixote of the world, but giving the weight of her moral sanction and support wherever she thinks that justice is, and wherever she thinks that wrong has been done... I say that it is a narrow policy to suppose that this country or that is to be marked out as the eternal ally or the perpetual enemy of England. We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow.... And if I might be allowed to express in one sentence the principle which I think ought to guide an English Minister, I would adopt the expression of Canning, and say that with every British Minister the interests of England ought to be the shibboleth of his policy.

Speech at dinner for West German Chancellor (Helmut Schmidt) (10 May 1979) http://www.margaretthatcher.org/document/104080
First term as Prime Minister
Context: It has been suggested by some people in this country that I and my government will be a “soft touch” in the [European] Community. In case such a rumour may have reached your ears, Mr Chancellor... it is only fair that I should advise you frankly to dismiss it (as my own colleagues did, long ago). We shall judge what British interests are and we shall be resolute in defending them.