Hungary lost of her land & of her population. I'm assuming this would be the reason why it's very hard to find genealogy records This is just so disturbing to those whose Hungarian bloodlines are now severely compromised. Such a wrongdoing!
Hungary, a reluctant player in WWI, paid a price no other modern nation had ever been subjected to. The Treaty of Versailles (Trianon) divided much Hungary's territory between Czechoslovakia, Austria, Yugoslavia and Romania.
The Holy Crown of Hungary, also known as the Crown of Saint Stephen According to tradition, any monarch who claims the Lands of the Crown of Saint Stephen without being crowned with the Holy Crown was and will never be legitimate