H. Beam Piper 
Space Viking 

Henry Beam Piper, (March 23, 1904 – c. November 6, 1964) was an American science fiction author. He wrote many short stories and several novels. He is best known for his extensive Terro-Human Future History series of stories and a shorter series of "Paratime" alternate history tales. "Space Viking" is a science fiction novel written by H. Beam Piper and is set in his Terro-Human future history. It tells the story of one man’s search for his wife’s murderer and its unexpected consequences. Ten thousand refugees from the losing side of The Big War (The System States War of The Cosmic Computer) fled far beyond the boundaries of the Terran Federation and colonised the planet Excalibur. By the beginning of Space Viking, they had expanded to a handful of Sword Worlds (so-called because they are named after legendary swords) and had grown to a total population of three and a half billion, organised in a feudal system of kingdoms, duchies, and other small states, ruled by frequently warring noblemen. Despite their isolation and the political instability, the inhabitants managed to retain a high level of technology, including space flight. (Excerpt from Wikipedia)