Address to the merchants of Philadelphia (16 May 1793), published in The Writings Of George Washington (1835) by Jared Sparks, p. 202 
1790s 
Context: The friends of humanity will deprecate War, wheresoever it may appear; and we have experience enough of its evils, in this country, to know, that it should not be wantonly or unnecessarily entered upon. I trust, that the good citizens of the United States will show to the world, that they have as much wisdom in preserving peace at this critical juncture, as they have hitherto displayed valor in defending their just rights.
                                    
        “My friends, as we enter a new decade, it should be clear to all of us that there is an unfinished agenda, that we have miles to go before we reach the promised land.
The men who rule this country today never learned the lessons of Dr. King, they never learned that non-violence is the only way to peace and justice.
Our nation continues to wage war upon its neighbors, and upon itself.”
    
    
    
    
        
        
        
            
            
        
        
        
        
        
        Lessons of Dr. Martin Luther King, Jr. (1990)
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Cesar Chavez 37
American farm worker, labor leader, and civil rights activi… 1927–1993Related quotes
                                        
                                        2013, Brandenburg Gate Speech (June 2013) 
Context: The wall belongs to history. But we have history to make as well. And the heroes that came before us now call to us to live up to those highest ideals -- to care for the young people who can't find a job in our own countries, and the girls who aren't allowed to go to school overseas; to be vigilant in safeguarding our own freedoms, but also to extend a hand to those who are reaching for freedom abroad. This is the lesson of the ages. This is the spirit of Berlin. And the greatest tribute that we can pay to those who came before us is by carrying on their work to pursue peace and justice not only in our countries but for all mankind.
                                    
2000s, 2001, Invasion of Afghanistan (October 2001)
Lessons of Dr. Martin Luther King, Jr. (1990)
“War should never be entered upon until every agency of peace has failed.”
                                        
                                        First Inaugural Address (March 4, 1897). 
1890s
                                    
“We don't wage war, but we are called upon to impose a peaceful solution”
                                        
                                        24 March 1999 on German television, quoted in the documentary film ‘Es begann mit einer Lüge’,  the complete manuscript of the film http://www.ag-friedensforschung.de/themen/NATO-Krieg/ard-sendung.html 
Context: We don't wage war, but we are called upon to impose a peaceful solution in Kosovo by military means as well.
                                    
1990s, Inaugural celebration address (1994)
“In life we never lose friends. We only learn what are the real we have.”
                                        
                                        Original: (it) Nella vita non perdiamo mai amici. Apprendiamo solo quali sono i veri che abbiamo. 
Source: prevale.net
                                    
1920s, Ways to Peace (1926)