“During war all institutions and organs of the State and of public opinion become, directly or indirectly, weapons of warfare. This is particularly true of the Press. No government carrying on a serious war will allow publications to exist on its territory which, openly or indirectly support the enemy.”

Armistice sermon The Unknown Soldier (preached Sunday 12 November 1933, immediately following Armistice Day), published in The Secret of Victorious Living (1934); also in I Renounce War : The Story of the Peace Pledge Union (1962) by Sybil Morrison. The sermon inspired Canon Dick Sheppard to write a letter to the press in 1934, leading to the founding of the Peace Pledge Union.

First Debate with Stephen Douglas in the Lincoln-Douglas debates http://www.bartleby.com/251/ of the 1858 campaign for the U.S. Senate, at Ottawa, Illinois (21 August 1858). Lincoln later quoted himself and repeated this statement in his first Inaugural Address (4 March 1861) to emphasize that any acts of secession were over-reactions to his election. During the war which followed his election he eventually declared the Emancipation Proclamation, freeing the slaves in those states in rebellion against the union, arguably as a war measure rather than as an entirely political or moral initiative.
1850s, Lincoln–Douglas debates (1858)

Scotland Live (2005-10-31): On the 2003 invasion of Iraq
2000s, 2005

Order of Retaliation http://quod.lib.umich.edu/l/lincoln/lincoln6/1:755?rgn=div1;view=fulltext (30 July 1863); quoted in Roy P. Basler, ed., The Collected Works of Abraham Lincoln, vol. 7 (New Brunswick, N.J.: Rutgers University Press, 1953), p. 357
1860s
Context: It is the duty of every government to give protection to its citizens, of whatever class, color, or condition, and especially to those who are duly organized as soldiers in the public service. The law of nations and the usages and customs of war as carried on by civilized powers, permit no distinction as to color in the treatment of prisoners of war as public enemies. To sell or enslave any captured person, on account of his color, and for no offence against the laws of war, is a relapse into barbarism and a crime against the civilization of the age. The government of the United States will give the same protection to all its soldiers, and if the enemy shall sell or enslave anyone because of his color, the offense shall be punished by retaliation upon the enemy's prisoners in our possession. It is therefore ordered that for every soldier of the United States killed in violation of the laws of war, a rebel soldier shall be executed; and for every one enslaved by the enemy or sold into slavery, a rebel soldier shall be placed at hard labor on the public works and continued at such labor until the other shall be released and receive the treatment due to a prisoner of war

1850s, Latter-Day Pamphlets (1850), Downing Street (April 1, 1850)

Source: Writings, The Institutes of Biblical Law (1973), p. 93

Method of Guerrilla Warfare (1963)

¶2. Published under "The Development of the American State," The State https://mises.org/library/state (Tucson, Arizona: See Sharp Press, 1998), p. 27.
"The State" (1918), II

The system of labor would have soon exhausted the soil and left the people poor. The non-slaveholders would have left the country, and the small slaveholder must have sold out to his more fortunate neighbor. Soon the slaves would have outnumbered the masters, and, not being in sympathy with them, would have risen in their might and exterminated them. The war was expensive to the South as well as to the North, both in blood and treasure, but it was worth all it cost.

Ch. 41
1880s, Personal Memoirs of General U. S. Grant (1885)