“One should be in harmony with, not in opposition to, the strength and force of the opposition.”

Nicomachus of Gerasa: Introduction to Arithmetic (1926)

Source: 1930s, A Dynamic Theory of Personality, 1935, p. 122.

Hays translation
XI, 18
Meditations (c. AD 121–180), Book XI

Source: 1960s, Strength to Love (1963), Ch. 1 : A tough mind and a tender heart
Context: The strong man holds in a living blend strongly marked opposites. The idealists are usually not realistic, and the realists are not usually idealistic. The militant are not generally known to be passive, nor the passive to be militant. Seldom are the humble self-assertive, or the self-assertive humble. But life at its best is a creative synthesis of opposites in fruitful harmony. The philosopher Hegel said that truth is found neither in the thesis nor the antithesis, but in the emergent synthesis which reconciles the two.

As translated by Philip Wheelwright in Heraclitus (1959) https://archive.org/details/heraclitus00whee
Disputed

Kalki : or The Future of Civilization (1929)
Context: War with its devastated fields and ruined cities, with its millions of dead and more millions of maimed and wounded, its broken-hearted and defiled women and its starved children bereft of their natural protection, its hate and atmosphere of lies and intrigue, is an outrage on all that is human. So long as this devil-dance does not disgust us, we cannot pretend to be civilized. It is no good preventing cruelty to animals and building hospitals for the sick and poor houses for the destitute so long as we willing to mow down masses of men by machine-guns and poison non-combatants, including the aged and the infirm, women and children — and all for what? For the glory of God and the honour of the nation!
It is quite true that we attempt to regulate war, as we cannot suppress it; but the attempt cannot succeed. For war symbolizes the spirit of strife between two opposing national units which is to be settled by force. When we allow the use of force as the only argument to put down opposition, we cannot rightly discriminate between one kind of force and another. We must put down opposition by mobilizing all the forces at our disposal. There is no real difference between a stick and a sword, or gunpowder and poison gas. So long as it is the recognized method of putting down opposition, every nation will endeavour to make its destructive weapons more and more efficient. War is its only law add the highest virtue is to win, and every nation has to tread this terrific and deadly road. To approve of warfare but criticize its methods, it has been well said is like approving of the wolf eating the lamb but criticizing the table-manners. War is war and not a game of sport to be played according to rules.

Source: One Flew Over the Cuckoo's Nest

Everything Has to Do with Hardness and Softness (1969)

Source: 1930s, The conflict between Aristotelian and Galileian modes of thought in contemporary psychology, 1931, p. 109 as cited in: Man Cheung Chung, Michael E. Hyland (2012) History and Philosophy of Psychology. p. 107.