“The world must remember that it was not simply international institutions — not just treaties and declarations — that brought stability to a post-World War II world. Whatever mistakes we have made, the plain fact is this: The United States of America has helped underwrite global security for more than six decades with the blood of our citizens and the strength of our arms.”

2009, Nobel Prize acceptance speech (December 2009)
Context: The world must remember that it was not simply international institutions — not just treaties and declarations — that brought stability to a post-World War II world. Whatever mistakes we have made, the plain fact is this: The United States of America has helped underwrite global security for more than six decades with the blood of our citizens and the strength of our arms. The service and sacrifice of our men and women in uniform has promoted peace and prosperity from Germany to Korea, and enabled democracy to take hold in places like the Balkans. We have borne this burden not because we seek to impose our will. We have done so out of enlightened self-interest — because we seek a better future for our children and grandchildren, and we believe that their lives will be better if others' children and grandchildren can live in freedom and prosperity.
So yes, the instruments of war do have a role to play in preserving the peace. And yet this truth must coexist with another — that no matter how justified, war promises human tragedy. The soldier's courage and sacrifice is full of glory, expressing devotion to country, to cause, to comrades in arms. But war itself is never glorious, and we must never trumpet it as such.