Ray Ortlund shares the following:
“The Ottomans did not follow up their decisive victory at [the battle of] Mohacs and advance further west. However, they did not want a new Catholic or Holy Roman army anywhere near their area. Now, it happened that a sizable Magyar, or native Hungarian, population of Protestants also lived in that area. So the Ottoman Muslims supported the Protestant Magyars! The Muslims saw the Protestants, most of whom were Reformed or Calvinist, as a buffer against the Holy Roman or Hapsburg emperor. So they not only tolerated the Hungarian Protestants; they encouraged them to thrive. This is why eastern Hungary and western Romania — the area known as Transylvania — are, right up through the present day, Calvinist. I myself believe Count Dracula was a Presbyterian.”
Paul F. M. Zahl, 2000 Years of Amazing Grace (Lanham, 2005), page 249.