“The Austrian Germans and Magyars will be set free and wreak a bloody revenge on the Slav barbarians. The general war which will then break out will smash this Slav Sonderbund and wipe out all these petty hidebound nations, down to their very names. The next classes and dynasties, but also of entire reactionary peoples. And that, too, is a step forward.”

Collected Works, Vol. 41, pp. 262–66
Collected Works

To the Foreign Minister of Bulgaria Solomon Pasi, in an interview to "Utrinski Vesnik" of Skopje on December 29,2001.

Marginal note to a memorandum written by Hellmuth Lucius von Stoedten (May 1918), quoted in Fritz Fischer, Germany's Aims in the First World War (New York: W. W. Norton & Co, 1967), p. 580
1910s

To Leon Goldensohn, March 16, 1946, from "The Nuremberg Interviews" by Leon Goldensohn, Robert Gellately - History - 2004

Epilogue to The Charge of the heavy Brigade, reported in Bartlett's Familiar Quotations, 10th ed. (1919)

Letter to Major R.M. Sawyer https://books.google.com/books?id=KZAtAAAAIAAJ&pg=PA280&lpg=PA280&dq=%22If+they+want+eternal+war%22&source=bl&ots=hqqkcQXgYR&sig=op8FljMWJcliz6HsZRrfGO9ShJs&hl=en&sa=X&ved=0ahUKEwjx38jz5KrKAhVHMz4KHbleCckQ6AEIIjAB#v=onepage&q=%22If%20they%20want%20eternal%20war%22&f=false (31 January 1864), from Vicksburg.
1860s, 1864, Letter to R.M. Sawyer (January 1864)
Context: p>If they want eternal war, well and good; we accept the issue, and will dispossess them and put our friends in their place. I know thousands and millions of good people who at simple notice would come to North Alabama and accept the elegant houses and plantations there. If the people of Huntsville think different, let them persist in war three years longer, and then they will not be consulted. Three years ago by a little reflection and patience they could have had a hundred years of peace and prosperity, but they preferred war; very well. Last year they could have saved their slaves, but now it is too late.All the powers of earth cannot restore to them their slaves, any more than their dead grandfathers. Next year their lands will be taken, for in war we can take them, and rightfully, too, and in another year they may beg in vain for their lives. A people who will persevere in war beyond a certain limit ought to know the consequences. Many, many peoples with less pertinacity have been wiped out of national existence.</p

Conversation with Thomas Jones (27 February 1932) after the Japanese invasion of Manchuria, quoted in Thomas Jones, A Diary with Letters. 1931-1950 (Oxford University Press, 1954), p. 30.
1932

1990s, Letter to the Union-Sun & Journal (1992)

from documentary Traceroute