Poul Anderson was famous for decades for writing hard sci-fi, with a good deal of violence even if it were not mil sci-fi.
He also wrote some fiction and fantasy about "the northern thing", set in various real or imaginary Dark Ages settings resembling northern Europe.
He seemed, to me, anyway, to have two layers of writing. One, to be uncharitable, would be called "potboiler" and the other his serious work. Dominic Flandry and the Polesotechnic League stories would fall, in my view, in the first. Avatar, Orion Shall Rise, Boat of A Million Years, in the second.
I preferred the former. The work I--although nobody I know has ever agreed with me--think of as being in the serious category was not particularly appealing, although Orion Shall Rise had some interesting situations.
Anderson's first categories had lessons relevant to the times. Appeasement doesn't work (Star Fox). Decadence will cost you an empire (Flandry). Socialism is soul-destroying and ruins economies and human freedom. (Polesotechnic League)
Star Fox has three main parts, each of which would be a decent novella, except for lacking a conclusion. The first is when the Bad Guys take a human colony. It's not just any colony. Anderson takes his beloved French countryside and makes an entire planet something like the Loire Vally with the French Alps on the side. The hero, Gunnar Heim, decides to buy and outfit a ship in order to go privateering against the Bad Guys, since the Terran government will do nothing. We see the man, his decision, his manuverings, the opposition in the United Nations.
The second part details the visit of the ship "Star Fox", to a planet where it would be loaded out with weapons not allowed to Heim by the Terran government. There are troubles galore including a trek across a hostile landscape. But the weapons are gained and then the Star Fox sets out. Strictly speaking, this part is not necessary, but is interesting.
The third part tells about the fighting, the talks between the representative of the Bad Guys and Heim, the work on the occupied colony planet, and the eventual victory.
Anderson does his usual superb job of setting scenes. I believe he once said that he rereads his manuscripts and, if he doesn't see a mention of a scent, odor, smell, fragrance, he puts one in. This is apparently the reason his characters are forever smoking pipes, drinking whiskey, smelling blood and spices.
If the book was to be an allegory about resisting evil regimes, it was at a time when the US' interest in such things was ebbing, even before Jimmy Carter.
Highly recommended, even if you're not in the market for an allegory about current events.