“We shall divert through our own Country a branch of commerce which the European States have thought worthy of the most important struggles and sacrifices, and in the event of peace… we shall form to the American union a barrier against the dangerous extension of the British Province of Canada and add to the Empire of liberty an extensive and fertile Country thereby converting dangerous Enemies into valuable friends.”

2016, Joint press conference of 17 November 2016

1860s, First State of the Union address (1861)

Radcliffe Commencement Address (16 June 1954), published as "The Illusion of Total Security" in The Atlantic Monthly, # 194 (August 1954)
Context: A foreign policy aimed at the achievement of total security is the one thing I can think of that is entirely capable of bringing this country to a point where it will have no security at all. And a ruthless, reckless insistence on attempting to stamp out everything that could conceivably constitute a reflection of improper foreign influence in our national life, regardless of the actual damage it is doing to the cost of eliminating it, in terms of other American values, is the one thing I can think of that should reduce us all to a point where the very independence we are seeking to defend would be meaningless, for we would be doing things to ourselves as vicious and tyrannical as any that might be brought to us from outside.
This sort of extremism seems to me to hold particular danger for a democracy, because it creates a curious area between what is held to be possible and what is really possible — an area within which government can always be plausibly shown to have been most dangerously delinquent in the performance of its tasks. And this area, where government is always deficient, provides the ideal field of opportunity for every sort of demagoguery and mischief-making. It constitutes a terrible breach in the dike of our national morale, through which forces of doubt and suspicion never cease to find entry. The heart of our problem, here, lies in our assessment of the relative importance of the various dangers among which we move; and until many of our people can be brought to understand that what we have to do is not to secure a total absence of danger but to balance peril against peril and to find the tolerable degree of each, we shall not wholly emerge from these confusions.

Letter to Sir Austen Henry Layard (20 October 1861) on the American Civil War, quoted in Jasper Ridley, Lord Palmerston (London: Constable, 1970), p. 552.
1860s

Knox to his wife, on the difficulties of dragging Cannon. Reported in David McCullough, 1776 (2005), p. 83.

1850s, Speech at Peoria, Illinois (1854)
Context: Our republican robe is soiled, and trailed in the dust. Let us repurify it. Let us turn and wash it white, in the spirit, if not the blood, of the Revolution. Let us turn slavery from its claims of “moral right,” back upon its existing legal rights, and its arguments of 'necessity'. Let us return it to the position our fathers gave it; and there let it rest in peace. Let us re-adopt the Declaration of Independence, and with it, the practices, and policy, which harmonize with it. Let north and south — let all Americans — let all lovers of liberty everywhere — join in the great and good work. If we do this, we shall not only have saved the Union; but we shall have so saved it, as to make, and to keep it, forever worthy of the saving. We shall have so saved it, that the succeeding millions of free happy people, the world over, shall rise up, and call us blessed, to the latest generations.

1970s, Second Inaugural Address (1973)

2000s, 2003, Invasion of Iraq (March 2003)

Speech to the Pembrokeshire Constituency Labour Party in Haverfordwest (26 July 1974), quoted in The Times (27 July 1974), p. 3
1970s