Undercurrents — Robert Buettner

Ace intelligence operative Lt. Jazen Parker parachutes into Tressen, a planet which resembles Earth in its Paleozoic era, on a mission to bring down the local politicos. He quickly realizes he's been handed a near-impossible task. Tressen is a politically-quarantined nightmare world with a culture confined to iron rivet technology and a ruling regime a bit to the right of Heinrich Himmler. Jazen's inclined to abandon this particular hellhole to its ways--that is, until he uncovers a plot afoot that will throw a five hundred-planet alliance into the death-throes of anarchy.

So the local Nazis must go. Unfortunately, all Jazen's got to work with is a handful of rust-bucket tanks, a retread rebellion, and two strong, beautiful women who love him, but think he's tilting at windmills and is about to get himself killed. What they don't know is, once committed, Jazen Parker is the best there is when it comes to getting the dirty job done on the ground. It's the local bullies who are about to be taught a lesson in losing.