The City Who Fought: Anne McCaffrey and S.M. Stirling

Book IV of Brainships. Simeon was bored with his life. It wasn't being a shell-person that bothered him - he rather pitied the 'softshells' with their short lives and their laughably limited senses - but the routine of running the mining and processing station that made up his 'body' was getting him down. So the excitement generated by the arrival of an out-of-control refugee ship was ore than welcome - even if it did interrupt his latest wargame. The refugees told of an attack by space barbarians who were headed Simeon's way, and it soon become apparent that if anyone was to survive Simeon had to translate his skills at wargaming into the real thing and become - THE CITY WHO FOUGHT. Cover art by Mark Harrison. https://cosmiccauldronbooks.com.au/p/ship-won-anne-mccaffrey-jody-lynn-nye/