The first piece of this fix-up ("Marque and Reprisal") was a Hugo nominee. For a coherent plot summary, I rely on P. Schuyler Miller, and quote from his review in Analog (February 1966):

"This book appeared in three sections, as separate novelettes in Fantasy and Science Fiction, early this year [1965]… In Part I, "Marque and Reprisal," space veteran and industrialist Gunnar Heim sees the World Federation about to abandon one of its frontier planets and half a million French colonists to the powerful, nonhuman Alerioina, who have decided to sweep Mankind out of Space and make the galaxy safe for the Alerian way of life. When logic fails, Gunnar Heim turns to more forceful means - necessarily so when militant pacifists kidnap his daughter as a hostage. And as a last resort, France commisions him a privateer, to rove Space at his own expense and prey on Alerian commerce and warcraft.

In Part II, "Arsenal Port," Gunnar is outfitting his ship on the arsenal world of the Staurni - a planet with a hydrogen atmosphere, where men must live in spacesuits. By itself, this part of the book would be a lively action story. Betrayed by the pacifists, Gunnar and a small party of friends and adversaries have to fight their way through the perils of the high-gravity world without ever leaving their suits. It is a classic obstacle-course yarn, handsomely developed, with ingenious applications of Staurn's built-in hazards, but as far as the book is concerned it is a scenic detour on Gunnar Heim's bumpy road to New Europe.

Part III, "Admiralty," finds him there and in contact with the refugees. The main thread of the plot gathers its legs under it (what a tangled metaphor!) and takes off - nor does it slow down for one moment, as Heim and his crew take on one menace after another in his private war against Alerion. There are all kinds of details and people to relish in the book, notably Endre Vadasz, the Hungarian minstrel who can draw on the ballads of scores of worlds. All through the book, through Endre's music, Poul Anderson shows you how important minstrels were in the quieter, more personal days of war and love and fellowship. And Cynbe ru Tauren, Intellect Master of the Alerion Garden of War and Gunnar's chief adversary, is another strong and subtle character whose real nature turns out to be the secret of his race and the key to his defeat. Nobody does this kind of story quite as well as Poul Anderson..." [P. Schuyler Miller]