Graustark - George Barr McCutcheon

The Graustark novels are stories of court intrigue, royal disguise, and romance similar to Anthony Hope's 1894 novel, The Prisoner of Zenda, and its sequels. They were popular best-sellers at the time they were published and the original editions are still readily available in used book shops. The novels gave their name to a fictional genre called Graustarkian: this genre contains tales of romance and intrigue usually featuring titled characters in small, fictional, Central European countries.
During the 1870's, Graustark's ruler, Prince Ganlook, was killed in a war with neighboring Axphain. As part of the ensuing peace treaty, Graustark agreed to pay a large indemnity to Axphain, to be due, with interest, in fifteen years. (Summary from Wikipedia)