The Day After Tomorrow (Sixth Column) by Robert A. Heinlein

I have always loved this book - and there are so many reasons that I shouldn't. It is totally misogynistic and racially bigoted. It is militaristic and elitist - and I could probably go on, but it is one of his best examples of pure "gee whiz" SF tech and that tech allows a initial corps of six men to recover the United States from a hostile take-over.

It was written shortly after the end of WWII and it was still probably acceptable to his readers to demonize orientals. He makes a mild case for American orientals - but he has the evil villains wipe them out - except for one fellow that manages to get to their hide-out. And after letting Mitsui ask the dumb questions so the white guys can explain the tech, he lets him die a hero. The premise is that at some point in the past the west cut off all contact with the far east, and in isolation this combined oriental race multiplied and suddenly attacked and devastated the US with a completely overwhelming force.

At one point, a couple of the good guys are discussing possibly recruiting women and decide against it. For one thing, they couldn't be allowed a public role in their game because the orientals despise women - but it is quite unclear that our heroes think much more of them than the evil yellow men. The orders go down, don't send any women, even to rescue them from forced prostitution.

But --- setting aside these few issues(?!) --- the solution they come up with is just a whole lot of fun. Although, and maybe this is one of its strengths, it really hardly qualifies as a novel - it is under 150 pages. Maybe his usual pontification got left on the cutting room floor.