I read this book about 10-Jan-2003. This is the first time I've read this book. The book is copyright 2002. This note was last modified Tuesday, 13-Jan-2004 13:01:40 PST.
This note contains spoilers for the book.
Another David Weber universe, and not as tired as the Honor Harrington one. Interesting structure to this book; we see the creation of a situation, and just before it cracks, we jump ahead to the consequences. It moves us around between tech levels a lot -- from 1340 to sometime a few centures in the future (I think a date is given, maybe twenty-seventh century, but it doesn't leap out at me scanning a few pages).
This book has some nice use of the primitive mercenaries in interstellar combat. Poul Anderson used a related idea (independents, not mercenaries) in The High Crusade, and a number of time-travel stories have been based on the idea scaled down to an individual. In this case it's because of rules about what sorts of force can be used on primitive planets. Importing Roman legions, or English bowmen on the way to France (probably for Agincourt?), can give a tremendous advantage to the people using them.
By the end, the Federation is pretty worried about Earth. Another strain this book exploits is the idea that things change fast on Earth (Harry Turtledove based his World War series around that idea too). Luckily, some Earthmen and some drones of another species have gone off and started a new empire, and it's prepared to stand up to the Federation. There could be more stories about this, too.