The Stoker and the Stars

This is short story book. When you've had your ears pinned back in a bowknot, it's sometimes hard to remember that an intelligent people has no respect for a whipped enemy… but does for a fairly beaten enemy. After an interstellar war (which Earth lost), contact with other stars is limited to trade. When a commercial freighter finds out what their new engine room mechanic used to be, they expect trouble with their old enemies. They get something else.