“Nothing in our Constitution is plainer than that declaration of a war is entrusted only to Congress. Of course, a state of war may in fact exist without a formal declaration. But no doctrine that the Court could promulgate would seem to me more sinister and alarming than that a President whose conduct of foreign affairs is so largely uncontrolled, and often even is unknown, can vastly enlarge his mastery over the internal affairs of the country by his own commitment of the Nation's armed forces to some foreign venture.”

"America First? America Last? America at Last?," Lowell Lecture, Harvard University (20 April 1992)
1990s

Regarding the Torture of Others (2004)

No. 78
The Federalist Papers (1787–1788)
Context: The complete independence of the Courts of justice is peculiarly essential in a limited Constitution. By a limited Constitution, I understand one which contains certain specified exceptions to the Legislative authority; such, for instance, as that it shall pass no bills of attainder, no ex post facto laws, and the like. Limitations of this kind can be preserved in practice no other way than through the medium of the Courts of justice; whose duty it must be to declare all Acts contrary to the manifest tenor of the Constitution void. Without this, all the reservations of particular rights or privileges would amount to nothing.

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.

Letter to his Manchester constituents defending his stance during the Don Pacifico affair of June 1850, quoted in G. M. Trevelyan, The Life of John Bright (London: Constable, 1913), p. 192.
1850s

2012, " The State of the Union is Still a State of War http://www.libertyforall.net/?p=7189"

While receiving a group of servicemen on the anniversary of the April victories of the Azerbaijani army (31 March 2017) http://en.apa.az/nagorno_karabakh/ilham-aliyev-nagorno-karabakh-conflict-is-azerbaijan-s-internal-affair.html
Nagorno-Karabakh

Enriquez responding to claims that the Chilean Military only intervened after the State declared the Salvador Allende government illegitimate.
Context: Today Chile is a country subjected by its Armed Forces to a regime similar to those that appeared in fascist occupied Europe. The country is under state of siege, all the cities under curfews, there are military tribunals established under the military code that like those established during times of war allow no appeal. There are mass arrest of the population and pogroms against foreigners, etc. The Chilean Armed Forces has declared war against the Chilean People…

Source: The Magic Mountain (1924), Ch. 6