A science fiction novel by Ben Bova. It's a great read, and features one of Bova's more used characters, Chet Kinsman. If you've read any of Bova's previous novels, you'll like this one. May remind fans of his newer books, Moonrise and Moonwar. I don't want to give too much of the plot away, but here's a synopsis from the back:

In a thriving colony far beneath
the ancient crater-marked crust of the Moon
the Russians and the Americans joined
together to launch the most daring offensive
ever against Earth in a desperate attempt
to save Man from himself...

Chet Kinsman
The American Chief had a daring
plan to avert the threatened war on Earth;
but he had only a handful of men-
and he hadn't counted on one of them being a traitor!

Ellen Berger
Had made the mistake of falling in love
with a man who loved his country enough to
risk death to try to save it!

Colonel Leonov
Commander of Lunagrad, the Russian sector of
Moonbase Selene, was a cool man under pressure...
until politics threatened to make sword enemies
out of his closest friends!