A Reminiscence Of Ferune

Poul Anderson, The High Crusade,  CHAPTER XVI.

See Hell Rock.

Deception continues. Having captured secret Wersgorix weapons, the English can present the secret weapons to other races as English. Sir Roger conceals his men's ignorance of spaceship weapons by deploying them in small fast craft.

A space battle resembles those in the Technic History (see the above link):

unimaginable distances;
fire-beams;
shells;
missiles;
artificial brains directing the ships;
artificial gravity;
ship sections self-sealing when damaged;
a mile-long, forcefield-protected flagship boarded by Sir Roger's space-armored, sword- and ax-wielding men who easily defeat a crew untrained in hand-to-hand combat - the hull is abandoned, then explodes.

"...many a sober, trustworthy man-at-arms swore that he saw [St. George] ride down the Milky Way in a foam of stars and impale enemy ships on his lance like so many dragons." (p. 121)

The Wersgorix, trapped by a surprise attack between their former colony planet and the allied fleet, suffer heavy losses and withdraw.