The Sixth Column by Robert A. Heinlein
The first published work by Robert Heinlein, originally as a serial in the pulps of the 1940s. Based on an outline by John Campbell, Heinlein took some of the edge off the overt racism in the outline. Keep in mind that was written in the 1940s and incidents such as the Rape of Nanking were know. It’s good Heinlein, not great Heinlein.