text: While serving as the king of another nation, a man from this nation won the Siege of Polotsk during the Livonian War.
full_question: While serving as the king of another nation, a man from this nation won the Siege of Polotsk during the Livonian War. A general from this nation waged the "Long Campaign" before losing the Battle of Varna. One king of this nation established a group of personal mercenaries known as the Black Army. Control of this home of John Hunyadi and Matthias Corvinus was split between the Ottomans and Transylvania after its ruler Louis II lost the Battle of Mohacs. This nation was unified by a king who also actively spread Christianity, Saint Stephen I. For 10 points, name this kingdom which is now a nation with a capital at Budapest.
first_sentence: While serving as the king of another nation, a man from this nation won the Siege of Polotsk during the Livonian War.
raw_answer: Kingdom of Hungary