The Iron Tactician, by Alastair Reynolds

A fun, bite-sized novella revisiting the adventures of Merlin of the Cohort as he continues his quest to find a weapon abandoned by a previous civilization that could tip the endless war against the Huskers in the Cohort’s favour. Here he finds himself interacting with a civilization in the midst of a civil war in the hopes of trading for a replacement for his faster-than-light artifact, which is no longer functioning as it should.