Pulp writer Robert E. Howard (1906-1936) is probably best known for his fantasy characters, especially of course Conan of Cimmeria--but he also wrote historical adventure. One of his best short stories is "Shadow of the Vulture", which concerns the story of one Gottfried von Kalmbach, a former Knight of Rhodes who was ousted from the Order for some nameless offense. Kalmbach finds himself contributing to the defense of Vienna in 1529, during the siege by Sulleyman the Magnificent. Along with von Kalmbach is a fierce female swordsman, Red Sonya (who was the inspiration for the later fantasy Marvel Comics heroine, Red Sonja). Red Sonya is sister to Roxelana, the Sultan's favorite wife. The villain is Mikhail Oglu, "Vulture of the Grand Turk", who leads the Ottoman's akincis light cavalry.
A great tale, if you can track it down.