Eric Thomson's military science-fiction series are set in the same universe, but not all in the same era.  Siobhan Dunmoore is a hard-charging warship captain caught in a stalemated war between the human Commonwealth and the alien Shrehari Empire.  If the enemy was all she had to worry about, life would be simple, but her worst foes sometimes wear the same uniform as she does.  Zack Decker is a former Marine pathfinder, an elite special operations trooper, who finds himself sucked into deep conspiracies to transform the Commonwealth into a repressive empire some seventy years after the armistice that ended the Shrehari war and left the Commonwealth in a perpetually unstable political balance.  Quis Custodiet follows the adventures of interstellar police officer Caelin Morrow and runs in parallel with Decker's War.  Ghost Squadron and Ashes of Empire bookend the era of humanity's thousand year interstellar empire, with the former describing its rise and the latter its destruction.