In 1526 the Ottomans destroyed the Hungarian army at Mohács, and within twenty years the kingdom had lost Buda and then Esztergom itself. The Archbishop of Esztergom moved north to Trnava, and suddenly there was nothing at all between the open lowland along the Nitra river and the Ottoman garrisons on the Danube. In 1545–46 Archbishop Pál Várdai had a fort thrown up on the left bank of the river; Archbishop Mikuláš Oláh strengthened it, which is why the Hungarian sources call it Oláhújvár, 'Oláh's new castle'. Everyone involved knew it was not strong enough.Roku 1526 rozdrvilo osmanské vojsko uhorskú armádu pri Moháči a do dvadsiatich rokov stratilo kráľovstvo Budín aj samotný Ostrihom. Ostrihomský arcibiskup sa presťahoval na sever do Trnavy a medzi otvorenou rovinou pri Nitre a osmanskými posádkami na Dunaji zrazu nestálo nič. V rokoch 1545 – 1546 dal arcibiskup Pavol Várdai narýchlo postaviť na ľavom brehu rieky pevnôstku a arcibiskup Mikuláš Oláh ju spevnil — po ňom sa jej hovorilo Oláhújvár, teda Oláhov nový zámok. Že to nestačí, vedeli všetci zúčastnení.
