Unio Trium Nationum (Latin for "Union of the Three Nations") was a pact of mutual aid codified in 1438 by three Estates of Transylvania: the (largely Hungarian) nobility, the Saxon (German) patrician class (represented by the Transylvanian Saxon University), and the free military Székelys. The union was directed against the whole of the peasantry, regardless of ethnicity, in response to the Transylvanian peasant revolt. In this typical feudal estate parliament, the peasants (whether Hungarian, Saxon, Székely, or Romanian in origin) were not represented, and they did not benefit from its acts, as the commoners were not considered to be members of these feudal "nations". Background Medieval administrative structure in Transylvania In medieval times, Transylvania was organised into two separate types of territorial units: the Noble Counties (Comitates) were ruled by feudal landlords. Here, the majority of population were Hungarian and Romanian serfs. In other regions called Seats, the free Székely and Saxon nations lived without feudal landlords and had the royal privilege to have local authority and self-government. Events leading to the Union With the rise of the Ottoman Empire, one of the first major Ottoman military campaigns against Transylvanian parts of the Kingdom of Hungary was organised in 1421. The invading forces entered the region from Wallachia. The Saxons and Székelys living in the border area tried to defend themselves, but were heavily outnumbered by the intruders. King Sigismund was not able to react promptly because he had recently inherited the Bohemian throne and was involved there in the Hussite Wars. Also, Transylvanian Diets had not been organized for decades and there was no forum to coordinate defence preparations of the three nations. Left alone, the Saxon Burzenland and the Székely Seat of Háromszék, both in the border region, were ravaged. Sigismund reacted to the attack only years later, leading a series of military campaigns against the Ottomans in Wallachia. The Ottomans, allied with the Wallachian Voivode, returned in 1432 and Southern Transylvania suffered serious damages again. In the same period, nobles and church authorities in Central Transylvania were concerned about protesting and revolting serfs. Hungarian and Romanian (Vlach) peasants were dissatisfied with high taxes and restrictions to their free movement. Scattered peasant protests turned into a serious revolt in 1437, when peasants and Hungarian nobles defeated the troops of the landholders. The Budai Nagy Antal Revolt was triggered by an attempt by the Bishop of Transylvania to collect