Rally Cry (Lost Regiment) 
Into this serfdom ruled by nobles and the Church, Keane and his men brought the radical ideas of freedom, equality, and democracyand a technology centuries ahead of the world they must now call home. Yet all their knowledge and training might not save them from the true rulers therecreatures to whom all humans were mere cattle, bred for sacrifice!
Reviews
But what no one has noticed is that the book is at least as enlightening on the subject of RUSSIAN history and society. The Tugar hordes are an alien race, but Forstchen's stroke of genius was to make them human by giving them the culture, outlook and capabilities of Genghis Khan's Mongol hordes. Note that this author bucks fifty years of Science Fiction convention here. These space aliens are not little green men with huge, bulging craniums and ray guns. Rather they are eight foot giants who despise all learning, technology, and even basic handicrafts. They are trapped in a nomadic, essentially sterile way of life that goes nowhere, and little by little in each book you sense their increasing pessimism and despair. Sustained brilliance by Forstchen makes these "hordes" into characters as compelling as any in the works of Larry McMurtry or James Fenimore Cooper. The hordes are doomed to extinction just like the noble red men of the American west.
Returning to the Mongol hordes analogy, however, what makes RALLY CRY such an eye-opening book is Forstchen's analysis of medieval Russia. Here THE KILLER ANGELS meets ALEKSANDER NEVSKY. Forstchen shows how the unhealthy alliance between boyars and the church, and the suffocation of the peasants, is a long-lasting after effect of the terrifying threat of Mongol invasion. Never before did I see quite so clearly how and why Russia evolved into a backwards, impoverished autocracy. The unspeakable horror of the Tugar feasts allows the nobility and the church to rule unquestioned and with no accountability to their own people. Though this is science fiction, it is also superb social commentary and insightful history.
This book is a classic -- even if you hate science fiction, you will love this!
