At length, after infinite effort, the two parties come into actual juxtaposition; and Thirty stands fronting Thirty, each with a gun in his hand. Straightway the word “Fire!” is given: and they blow the souls out of one another; and in place of sixty brisk useful craftsmen, the world has sixty dead carcasses, which it must bury, and anew shed tears for. Had these men any quarrel? Busy as the Devil is, not the smallest! They lived far enough apart; were the entirest strangers; nay, in so wide a Universe, there was even, unconsciously, by Commerce, some mutual helpfulness between them. How then? Simpleton! their Governors had fallen-out; and, instead of shooting one another, had the cunning to make these poor blockheads shoot.

Thomas Carlyle (1795-1881) Scottish essayist and historian

Sartor Resartus, Book 2, ch. 8 (1834)
    (Source)

Quoting Herr Teufelsdröckh, describing thirty English village boys from Dumdrudge being sent to war and encountering thirty boys from a similar French village.

This passage first appeared in Fraser's Magazine for Town and Country, Vol. 9, No. 52 (1834-04).

Emma Goldman in her lecture (1908-04-26), "Patriotism: A Menace to Liberty," given at Walton's Pavilion, San Francisco, appears to paraphrase this, while attributing it as an (unsourced) quote from Carlyle:

War is a quarrel between two thieves too cowardly to fight their own battle; therefore they take boys from one village and another village, stick them into uniforms, equip them with guns, and let them loose like wild beasts against each other.