Peace cannot be kept by force; it can only be achieved by understanding.

We traced this line to Albert Einstein's address to the New History Society in New York on December 14, 1930, published the following year as "Militant Pacifism" in Cosmic Religion, with Other Opinions and Aphorisms (Covici-Friede, 1931; Dover reprint, 2009, p. 67). The sentence opens a longer passage that continues: "You cannot subjugate a nation forcibly unless you wipe out every man, woman, and child. Unless you wish to use such drastic measures, you must find a way of settling your disputes without resort to arms." The full passage appears with this provenance in Alice Calaprice's The Quotable Einstein (Princeton University Press), a rigorously sourced compilation. Notably, the quotation does not appear in the better-known Einstein collections — Ideas and Opinions*,* The World As I See It*, or* Einstein on Peace — which is why it is often circulated without a citation and sometimes vaguely credited to "an interview"; Cosmic Religion is a separate 1931 volume and is the correct source. The wording here matches the published text, though shortened variants (including "achieved through understanding") circulate widely. On the strength of a publication issued in Einstein's lifetime under his name, with a specific page reference and corroboration in scholarly compilation, we are marking this quotation as verified.