Great story--as usual--by Mercedes Lackey.
TRAINING THE ENEMY
Alverich had spent most of his youth in the Karsite military schools training to be an officer. As the son of an impoverished mother, he had had no other career choice open to him. And Alberich had risen in the ranks with almost unnatural speed. He developed expertise with many weapons and excelled in academic subjects with an ease that was the envy of his classmates. But in fact, the reclusive Alberich studied long and hard, pushing himself ruthlessly.
In battle, Alberich had always had a sort of "sixth sense" about things which were about to happen--when and from where the enemy would attack. Instinctively, he hid this ability, for the Sunpriests kept careful watch for anyone exhibiting the "demon powers" which were the hallmark of Karse's greatest enemy--the witch-nation of Valdemar. Those they caught were "cleansed" in the fires of Vkandis Sunlord.
Both Alberich's skill and secret served him well in the army of Karse, and when Alberich became one of Karse's youngest captains, he received a special gift--a powerful white stallion "liberated from the enemy." But this honor was merely a distraction, for the Sunpriests had laid a trap which even Alberich's strange foresight could not predict...
Saved from burning as a witch when his odd white stallion braved the flames and carried him over the border into Valdemar, he was healed by the same enemies he had been taught to hate his entire life. Though he knew he could never again return to his home, Alberich also knew he could never truly become a Valdemaran. How could Alberich remain true to his own people and still retain his honor while helping to train the direst enemy of Karse?
One of my favorite books in the Valdemar series. You will fall in love with the many interesting and colorful characters. Exciting and fast paced story. You won't want to put it down! The sequel is Exile's Valor. Be sure to also read Take a Thief after these two!