“Surely you do not imagine that we shall be victorious without applying the most cruel revolutionary terror?”

Volume 3, Ch. 17
Fiction, The Book of the Short Sun (1999–2001)

Directives Regarding the Cultural Revolution (1966-1972)

Lecture II, section 35.
The Eagle's Nest (1872)
Context: We shall be remembered in history as the most cruel, and therefore the most unwise, generation of men that ever yet troubled the earth: — the most cruel in proportion to their sensibility, — the most unwise in proportion to their science. No people, understanding pain, ever inflicted so much: no people, understanding facts, ever acted on them so little.

1850s, The House Divided speech (1858)
Context: Of strange, discordant, and even hostile elements, we gathered from the four winds, and formed and fought the battle through, under the constant hot fire of a disciplined, proud, and pampered enemy. Did we brave all them to falter now? — now, when that same enemy is wavering, dissevered, and belligerent? The result is not doubtful. We shall not fail — if we stand firm, we shall not fail. Wise counsels may accelerate, or mistakes delay it, but, sooner or later, the victory is sure to come.

Speech in the House of Commons, after taking office as Prime Minister (13 May 1940) This has often been misquoted in the form: "I have nothing to offer but blood, sweat and tears ..."
The Official Report, House of Commons (5th Series), 13 May 1940, vol. 360, c. 1502. Audio records of the speech do spare out the "It is" before the in the beginning of the "Victory"-Part.
The Second World War (1939–1945)
Context: You ask, what is our policy? I will say: It is to wage war, by sea, land and air, with all our might and with all the strength that God can give us: to wage war against a monstrous tyranny, never surpassed in the dark, lamentable catalogue of human crime. That is our policy. You ask, what is our aim? I can answer in one word: It is victory, victory at all costs, victory in spite of all terror, victory, however long and hard the road may be; for without victory, there is no survival.
Context: I would say to the House, as I said to those who have joined this Government: 'I have nothing to offer but blood, toil, tears, and sweat.' We have before us an ordeal of the most grievous kind. We have before us many, many long months of struggle and of suffering. You ask, what is our policy? I will say: It is to wage war, by sea, land and air, with all our might and with all the strength that God can give us: to wage war against a monstrous tyranny, never surpassed in the dark, lamentable catalogue of human crime. That is our policy. You ask, what is our aim? I can answer in one word: It is victory, victory at all costs, victory in spite of all terror, victory, however long and hard the road may be; for without victory, there is no survival.

Also misnaming Zubatov: in one source his initials are TC, in the other - Z.B. (his actual initials are S.V.).
The actual origin is unknown.
Misattributed
Source: [Wolf, Paul, COINTELPRO: The Untold American Story, https://archive.org/stream/CointelproTheUntoldAmericanStory/COINTELPRO#page/n11/mode/2up, Archive.org, World Conference Against Racism, Durbin SA]
Source: Missouri Law Review, Volume 70, Issue 2, Spring 2005: Sting Operations, Undercover Agents and Entrapment: by Bruce Hay http://scholarship.law.missouri.edu/cgi/viewcontent.cgi?article=3652&context=mlr

"On the Principles of Political Morality that Should Guide the National Convention in the Domestic Administration of the Republic" (5 February 1784/18 Ploviôse Year 2)
"On the Principles of Political Morality"

With the century, vol. 1