Sixth Column, also known under the title The Day After Tomorrow, is a science fiction novel by American writer Robert A. Heinlein, based on a then-unpublished story by editor John W. Campbell, and set in a United States that has been conquered by the PanAsians, who are asserted to be neither Japanese nor Chinese.

A top secret research facility hidden in the Colorado mountains is the last remaining outpost of the United States Army after its defeat by the PanAsians.

"[3] P. Schuyler Miller compared Sixth Column to "the old E. Phillips Oppenheim or modern Eric Ambler intrigue, thrust and counterthrust with civilization at stake.

"[4] The book was serialized in early 1941, at a time that the Second Sino-Japanese War was in its fourth year and large parts of China had been occupied in brutal fashion by the Japanese.

They demand outward signs of respect, such as jumping promptly into the gutter when a member of the chosen race walks by, and the slightest hesitation to show the prescribed courtesies earns a swagger stick across the face.