G. A. Henty 
With Frederick The Great [EPUB ebook] 

Among the great wars of history there are few, if any, instances of so      
long and successfully sustained a struggle, against enormous odds,      
as that of the Seven Years’ War, maintained by Prussia—then a small      
and comparatively insignificant kingdom—against Russia, Austria,      
and France simultaneously, who were aided also by the forces of      
most of the minor principalities of Germany.