Education is the cheap defence of nations.

Edmund Burke (1729-1797) Anglo-Irish statesman, orator, philosopher

(Spurious)

American spelling variant: "Education is the cheap defense of nations."

While widely quoted since the early 19th Century, there is no record of Burke having said or written it. The earliest references come from Thomas Chalmers (1827, 1832), who mentions it as a well-known quotation, but many other uses of it show up quickly after (1835, 1837, 1838, 1839, etc.), continuing through the 19th and early 20th centuries.

Burke did, in Reflections on the Revolution in France (1790), make a reference to the "cheap defence of nations," but in the very different context of praising the social order of genteel nobility and honor. In a passage bemoaning the execution of Marie Antoinette, he wrote (emphasis mine):

But the age of chivalry is gone; that of sophisters, economists, and calculators has succeeded, and the glory of Europe is extinguished forever. Never, never more, shall we behold that generous loyalty to rank and sex, that proud submission, that dignified obedience, that subordination of the heart, which kept alive, even in servitude itself, the spirit of an exalted freedom! The unbought grace of life, the cheap defense of nations, the nurse of manly sentiment and heroic enterprise is gone. It is gone, that sensibility of principle, that chastity of honor, which felt a stain like a wound, which inspired courage whilst it mitigated ferocity, which ennobled whatever it touched, and under which vice itself lost half its evil, by losing all its grossness.

It's unclear how this phrase got "Education is ..." grafted to it, though some see it as an intentional and nefarious fabrication.