make common cause

Possibly a calque of French faire cause commune, first attested in the same period (1787).[1]

make common cause (third-person singular simple present makes common cause, present participle making common cause, simple past and past participle made common cause)

1. To cooperate, to enter into an alliance for a shared goal.
   • 1786, Philip Francis, Speech in the House of Commons, on Tuesday the 7th of March, 1786, London: J. Debrett, p. 35,

     […] in a great community, the reformer has the voice and approbation of a majority to encourage him. In a very narrow circle he will have no part of the society, in which he lives, to support him against the rest. They will all make common cause against him, and sooner or later overcome his resolution, or break his heart.

   • 1859, John Stuart Mill, On Liberty, London: John W. Parker & Son, Introductory, p. 18,

     They preferred endeavouring to alter the feelings of mankind on the particular points on which they were themselves heretical, rather than make common cause in defence of freedom, with heretics generally.

   • 1910, Annie Marion MacLean, Wage-Earning Women, New York: Macmillan, Chapter 10, p. 161,

     The factory girl, the shop girl, the college girl, the woman in the home, the woman active in public welfare, and the woman in society, as well as all the men in the nation, should make common cause of race improvement, and no far-reaching improvement is possible while young girls are allowed to exhaust their physical energy and jeopardize their moral integrity in occupations where the remuneration practically precludes a normal standard of life.

   • 2009, Alice Munro, “Face” in Too Much Happiness, Toronto: McClelland & Stewart, p. 145,

     We were both flawed, obvious victims of physical misfortune. You would think such people would make common cause, but it could just as often happen that they don’t. Each may be reminded by the other of something sooner forgotten.

Often used in the phrases make common cause with and make common cause against.

• join forces
• team up

• common cause