“If civilization is to survive, the principles of the Prince of Peace must be restored. Shattered trust between nations must be revived. Most important of all, the will for peace on the part of peace-loving nations must express itself to the end that nations that may be tempted to violate their agreements and the rights of others will desist from such a cause. There must be positive endeavors to preserve peace.”

1860s
Context: There is no doubt that all nations are aggressive; it is the nature of man. There start up from time to time between countries antagonistic passions and questions of conflicting interest, which, if not properly dealt with, would terminate in the explosion of war. Now, if one country is led to think that another country, with which such questions might arise, is from fear disposed on every occasion tamely to submit to any amount of indignity, that is an encouragement to hostile conduct and to extreme proceedings which lead to conflict. It may be depended on that there is no better security for peace between nations than the conviction that each must respect the other, that each is capable of defending itself, and that no insult or injury committed by the one against the other would pass unresented.

Speech http://hansard.millbanksystems.com/commons/1862/feb/17/obsebvations in the House of Commons (17 February 1862).

Speech to the Labour Party Conference in Caxton Hall, London (12 December 1944), quoted in The Times (13 December 1944), p. 2.
War Cabinet

As quoted in Global History, Volume Two : The Industrial Revolution to the Age of Globalization (2008) by Jerry Weiner, Mark Willner, George A. Hero and Bonnie-Anne Briggs, p. 175
Context: Mexicans: let us now pledge all our efforts to obtain and consolidate the benefits of peace. Under its auspices, the protection of the laws and of the authorities will be sufficient for all the inhabitants of the Republic. May the people and the government respect the rights of all. Between individuals, as between nations, peace means respect for the rights of others.

2000s, 2004, Speech to United Nations General Assembly (September 2004)

Kennedy's "focus on a more practical, more attainable peace, based not on a sudden revolution in human nature but on a gradual evolution of human institutions." was quoted by Barack Obama in his Nobel Prize acceptance speech.
1963, American University speech
Context: I am not referring to the absolute, infinite concept of peace and good will of which some fantasies and fanatics dream. I do not deny the value of hopes and dreams but we merely invite discouragement and incredulity by making that our only and immediate goal. Let us focus instead on a more practical, more attainable peace — based not on a sudden revolution in human nature but on a gradual evolution in human institutions — on a series of concrete actions and effective agreements which are in the interest of all concerned. There is no single, simple key to this peace — no grand or magic formula to be adopted by one or two powers. Genuine peace must be the product of many nations, the sum of many acts. It must be dynamic, not static, changing to meet the challenge of each new generation. For peace is a process — a way of solving problems.

Remarks by President Obama in Address to the United Nations General Assembly (24 September 2013) http://www.whitehouse.gov/the-press-office/2013/09/24/remarks-president-obama-address-united-nations-general-assembly
2013

Address to Congress (1945)
Context: If wars in the future are to be prevented the nations must be united in their determination to keep the peace under law.
Nothing is more essential to the future peace of the world than continued cooperation of the nations which had to muster the force necessary to defeat the conspiracy of the Axis powers to dominate the world.
While these great states have a special responsibility to enforce the peace, their responsibility is based upon the obligations resting upon all states, large and small, not to use force in international relations except in the defense of law. The responsibility of the great states is to serve and not to dominate the world.

Some Reflections on Peace in Our Time (1950)
Context: There can be peace and a better life for all men. Given adequate authority and support, the United Nations can ensure this. But the decision really rests with the peoples of the world. The United Nations belongs to the people, but it is not yet as close to them, as much a part of their conscious interest, as it must come to be. The United Nations must always be on the people's side. Where their fundamental rights and interests are involved, it must never act from mere expediency. At times, perhaps, it has done so, but never to its own advantage nor to that of the sacred causes of peace and freedom. If the peoples of the world are strong in their resolve and if they speak through the United Nations, they need never be confronted with the tragic alternatives of war or dishonourable appeasement, death, or enslavement.

1990s, Inaugural celebration address (1994)
Context: We are both humbled and elevated by the honour and privilege that you, the people of South Africa, have bestowed on us, as the first President of a united, democratic, non-racial and non-sexist government.
We understand it still that there is no easy road to freedom
We know it well that none of us acting alone can achieve success.
We must therefore act together as a united people, for national reconciliation, for nation building, for the birth of a new world.
Let there be justice for all.
Let there be peace for all.