“Denounce treason and uphold the cause of the Union.”
As quoted in Indiana in the Civil War Era, 1850–1880: History of Indiana III https://en.wikiquote.org/wiki/Special:BookSources/0871950502 (1995), by Emma Lou Thornbrough. Indianapolis: Indiana Historical Society, p. 102
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Oliver P. Morton 6
American politician 1823–1877Related quotes

The Canton, Ohio Speech, Anti-War Speech (1918)
Context: And now for all of us to do our duty! The clarion call is ringing in our ears and we cannot falter without being convicted of treason to ourselves and to our great cause.
Do not worry over the charge of treason to your masters, but be concerned about the treason that involves yourselves. Be true to yourself and you cannot be a traitor to any good cause on earth.
Yes, in good time we are going to sweep into power in this nation and throughout the world. We are going to destroy all enslaving and degrading capitalist institutions and re-create them as free and humanizing institutions. The world is daily changing before our eyes. The sun of capitalism is setting; the sun of socialism is rising. It is our duty to build the new nation and the free republic.

1860s, The Prayer of the Twenty Millions (1862)

“Our cause is just, our union is perfect.”
Declaration on taking up Arms in 1775. From the original manuscript draft in Dickinson's handwriting, which has given rise to the belief that he, not Jefferson (as formerly claimed), is the real author of this sentence.

Riel, notre frère, est mort, victime de son dévouement à la cause des Métis dont il était le chef, victime du fanatisme et de la trahison; du fanatisme de Sir John et de quelques-uns de ses amis; de la trahison de trois des nôtres qui, pour garder leur portefeuille, ont vendu leur frère.
Speech of 1885 about the hanging of Louis Riel, at the Champs de Mars of Montreal. http://www.ledevoir.com/2003/08/25/34656.html

As his enemies dared riot meet the challenge, he was acquitted.
1920s, Ordered Liberty and World Peace (1924)

1860s, The Prayer of the Twenty Millions (1862)

Cap. X - Bay of Pigs: On March 29, 1961 Senator Fulbright gave Kennedy a memorandum opposing moral and legal grounds.
A Thousand Days:John F.Kennedy in the White House (1965)

Source: Speech in the Star Chamber at the censure of John Bastwick, Henry Burton and William Prynne (16 June 1637), quoted in The Works of the Most Reverend Father in God, William Laud, sometime Lord Archbishop of Canterbury. Volume VI: Part I (1847), p. 42