“As long as 1911, when I was still a member of the Socialist Party, I wrote that the Gordian knot of Trent could be cut only by the sword. At the same date I declared that war is usually the prelude to revolution. It was therefore easy for me, when the Great War broke out, to predict the Russian and the German revolutions.”

"Charity Overcoming Envy"
The Poems of Marianne Moore (2003)

Waldersee in his diary, 15 October 1885, quoted in Scott A. Silverstone, From Hitler's Germany to Saddam's Iraq

1930s, From the film Triumph of the Will (1935)

Source: Marcelo H. del Pilar, "Our Anxieties", La Solidaridad, Year VII. No.64 (15 September 1891)
Context: This called for more endurance and patience on their part while peaceful processes were being carried out.

Source: The Lowland

Hansard, House of Commons, 5th series, vol. 376, col. 1336.
Speech in the House of Commons, 4 December 1941.

Source: The Managerial Revolution, 1941, p. 220–221; As cited in Marcel van der Linden (2007, p. 83)

“Lessons of the Commune”, in Zagranichnaya Gazeta, No. 2 (23 March 1908) http://www.marx.org/archive/lenin/works/1908/mar/23.htm, as translated by Bernard Isaacs, Collected Works, Vol. 13, p. 478.
1900s
Variant: The proletariat should not ignore peaceful methods of struggle — they serve its ordinary, day-to-day interests, they are necessary in periods of preparation for revolution — but it must never forget that in certain conditions the class struggle assumes the form of armed conflict and civil war; there are times when the interests of the proletariat call for ruthless extermination of its enemies in open armed clashes. This was first demonstrated by the French proletariat in the Commune and brilliantly confirmed by the Russian proletariat in the December uprising.

Source: Property and Freedom (1999), p. 220