“The army must become one with the people so that they see it as their own army. Such an army will be invincible, and an imperialist power like Japan will be no match for it.”

On Coalition Government (1945)

Radio Address https://www.marxists.org/reference/archive/stalin/works/1941/07/03.htm (3 July 1941)
Stalin's speeches, writings and authorised interviews

Source: attributed and quoted in M.A. Khan , Islamic Jihad: A legacy of forced conversion, imperialism and slavery (2011)

The wars of the past show us that even armies that had won brilliant victories for decades, in some cases were not only defeated but even disintegrated and ceased to exist. Such a fate, for example, befell the army of Napoleon, who for almost two decades kept the whole Europe under its boots. The army needs to instill a spirit of confidence in its power, but not in terms of boasting. Bragging about invincibility brings harm to the army.
Speech to Red Army personnel, 13 May 1940
Source: http://porto-fr.odessa.ua/index.php?art_num=art021&year=2008&nnumb=40

49
Multitude: War and Democracy in the Age of Empire

What I Believe (1938)
Context: On they go — an invincible army, yet not a victorious one. The aristocrats, the elect, the chosen, the Best People — all the words that describe them are false, and all attempts to organize them fail. Again and again Authority, seeing their value, has tried to net them and to utilize them as the Egyptian Priesthood or the Christian Church or the Chinese Civil Service or the Group Movement, or some other worthy stunt. But they slip through the net and are gone; when the door is shut, they are no longer in the room; their temple, as one of them remarked, is the holiness of the Heart's affections, and their kingdom, though they never possess it, is the wide-open world.
With this type of person knocking about, and constantly crossing one's path if one has eyes to see or hands to feel, the experiment of earthly life cannot be dismissed as a failure. But it may well be hailed as a tragedy, the tragedy being that no device has been found by which these private decencies can be transmitted to public affairs. As soon as people have power they go crooked and sometimes dotty as well, because the possession of power lifts them into a region where normal honesty never pays.

Variant translation: Two armies that fight each other is like one large army that commits suicide.
Under Fire (1916), Ch. 1 - The Vision

Remarks by el-Sisi on Sinai liberation celebrations day (28 April 2013) http://www.youtube.com/watch?v=-x1xN8LUYG4.
2013

To his mother (1997), as quoted in American Terrorist: Timothy McVeigh and the Oklahoma City Bombing https://en.wikiquote.org/wiki/Special:BookSources/0060394072 (2001), by Lou Michel and Dan Herbeck, New York: ReganBooks (HarperCollins), p. 347.
1990s