Coined in 1966 at the start of the Cultural Revolution. The
四旧 referred to:
旧思想 (old ideas),
旧文化 (old culture),
旧风俗 (old customs),
旧习惯 (old habits). Red Guards (
红卫兵) used the slogan
破四旧 ('smash the Four Olds') to justify destroying temples, books, art, and persecuting intellectuals.