The diet sessions at Vásárhely (now Târgu Mureș) (20 January 1542) and at Torda (now Turda) (2 March 1542) laid the basis for the political and administrative organization of Transylvania.
[15] Thereafter, only the wealthiest Székelys fought in the royal army on horse; those who could only fight as foot-soldiers started to lose their political rights.
[19] However, the wealth of the Saxon merchants, who controlled the trade routes towards Wallachia and Moldavia, enabled them to gradually achieve the restoration of their autonomy.
[24] The Romanian districts were initially located in royal estates, but most of them were given away to noblemen or prelates by the end of the Middle Ages, or the local chiefs (or knezes) achieved the acknowledgement of their ownership from the kings.
[25][26] General assemblies of the noblemen from one or more counties developed into important forums of the administration of justice in the entire Kingdom of Hungary in the second half of the 13th century.
[36][37] The assembly authorized the vice-voivode, Ladislaus Borsa, to assist the representative of Peter Monoszló, Bishop of Transylvania, in taking possession of three villages of a noble family to secure the payment of a fine.
[36][37] The administration of justice remained the principal task of such meetings, but the noblemen who attended the assemblies also regularly discussed other subjects, including the collection of the tithe or custom duties.
[40] From 1486, the Count of the Saxons presided over the annual general assemblies of the entire community, which consisted of the highest-ranking officials of the seats and districts and elected delegates.
[35] Andrew III of Hungary was the first king to hold such an assembly for the representatives of the Transylvanian noblemen, Saxons, Székelys and Romanians in early 1291.
[42][43] According to Andrew's charter mentioning the meeting, the king ordered the return of two domains to Ugrin Csák after those who attended the general assembly testified that he had been their lawful owner.
[44][45] After George Lépes, Bishop of Transylvania, demanded the payment of the tithe that he had failed to collect in the previous years, thousands of Hungarian and Romanian commoners and lesser noblemen took up arms against him in early 1437.
[46][47] Without seeking royal authorization, the vice-voivode convoked the noblemen and the leaders of the Székelys and Saxons to hold a joint assembly at Kápolna (now Căpâlna in Romania).
[46][48] At the meeting, the representatives of the noblemen, Székelys and Saxons concluded a "brotherly union" on 16 September, pledging to provide assistance to each other against their internal and external enemies.
[46][48] The agreement of the three privileged groups gave rise to the idea of the "Union of the Three Nations of Transylvania",[49][50] which replaced the previous concept about the three Transylvanian regions (that is, the counties, and the Székely and Saxon seats).
[54][51] The regular meetings of the delegates of the Three Nations developed into "Transylvania's foremost representative" assemblies,[55] providing basis for the Transylvanian Diet.
[58] When writing of the regnum Transylvanum, the royal charters initially referred to the Transylvanian noblemen[58] who formed a closed community "bound together by certain reciprocal rights and duties".
...[A]lthough the ... Transylvanians have various customs quite different from ours regarding the payment of man-price and fines and in certain other legal procedures and in the observing of [judicial] terms..., and have the right to use and enjoy these customs, and are allowed, even now, with the [monarch's] consent, to make statues and ordinances among themselves on similar matters; nevertheless, they cannot establish any law and they have no right to make statutes in contravention of general statutes and decrees of this kingdom of Hungary or against sentences and judicial decisions in cases of goods and property rights which are usually made, passed and pronounced in the royal court by justices ordinary.The Ottoman Sultan, Suleiman the Magnificent, annihilated the royal army in the Battle of Mohács on 29 August 1529.
[65][66] The majority of the noblemen elected the voivode of Transylvania, John Zápolya, king, but the wealthiest magnates offered the throne to Louis II's brother-in-law, Ferdinand of Habsburg, Archduke of Austria.
[65][66] During the ensuing civil war, the medieval Kingdom of Hungary was actually divided into two parts, with John Zápolya controlling the eastern regions, including Transylvania.
[74] Thereafter he was styled prince of Transylvania, but his successors' right to use the new title was acknowledged by the Habsburg rulers of Royal Hungary only in 1595, during the reign of Sigismund Báthory.
[78] The noblemen (the "Hungarian nation") dominated the Diets, but the Székelys' military power and the Saxons' wealth secured the effective protection of their interests.
[97] The second or "short Diet" was customarily held around the feast of Saint Michael (29 September), but Gabriel Bethlen persuaded the Estates to cancel it in 1622.
[99] Although the town had customarily been the Transylvanian rulers' seat, the delegates preferred Torda, Kolozsvár and Nagyenyed (now Cluj-Napoca and Aiud in Romania), which were located in the central region of the principality.
[99] Frequent invasions forced Michael I Apafi to convoke the Diets to the fortresses of Fogaras and Radnót (now Făgăraș and Iernut in Romania) in the late 1680s.
[101] Most instructions concerned local issues (such as trade privileges and conflicts between burghers and noblemen), enabling the delegates to freely discuss general topics.
[103] For instance, when Michael I Apafi tried to persuade the Diet to pass decrees concerning issues which had not been mentioned in his letter of invitation, the delegates resisted, saying that their instructions did not cover these topics.
[104] The delegates of each Nation or denomination could hold separate meetings before the opening to draft their own proposals on specific issues relating to their community.
[111] The negotiations preceding a prince's election enabled the Three Nations to secure the issue of a specific charter in which the future monarch pledged to respect their liberties.
[119] On the other hand, the Diets passed hundreds of decrees about issues of local interest, including the regulation of the quest for runaway serfs or of the boundaries of noble estates.
[122] The Diets sometimes entered into direct correspondence with foreign powers, but the letters evidence that the support of the monarchs' specific diplomatic acts was the delegates' principal purpose.