Union of Lublin
The Union of Lublin (Lithuanian: Liublino unija; Belarusian: Лю́блінская ву́нія; Polish: Unia lubelska) – signed on July 1 1569 in Lublin, united the Kingdom of Poland and the Grand Duchy of Lithuania into a single state, the Polish-Lithuanian Commonwealth, with the official name: Rzeczpospolita Obojga Narodów (also known as The Republic of Both Nations). The Commonwealth was ruled by a single elected monarch who took the duties of the Polish king and the Lithuanian grand duke, and governed by a common diet and senate (known as the Sejm). The Union was a development of the Polish-Lithuanian alliance and personal union, and further necessitated by Lithuania's dangerous position in wars with Russia.
There were long discussions before signing the treaty, as Lithuanian magnates were afraid of losing much of their powers, since the union would make their status equal in the eyes of law with that of the much more numerous lower nobility. When Polish nobles (the szlachta) saw that the Lithuanians might not sign the union, Poland occupied the southern Lithuanian-controlled lands of Podlachia, Volhynia, Podolia and the Kyiv regions (these lands makes up more than half of modern day Ukraine, and were at that time a significant part of Lithuanian territory).
The Lithuanian nobles then signed the treaty, since Lithuania faced the threat of total defeat in the Livonian war against Russia and incorporation into the Russian Empire. Poland provided military aid in that war after the union of the two entities, but did not return the previously annexed territories. Lithuania had to recognise its incorporation into Poland. After the Union, Lithuanian nobles had the same rights as Polish to exploit the territories of the Commonwealth.
The drafters of the Union of Lublin expected that the countries of Lithuania and Poland should be linked together more closely than they actually were, because the Second statute of Lithuania had not lost its power, and some of its provisions substantially differed from the acts of Union of Lublin. Eventually the Third statute of Lithuania was adopted, which however still contradicted the Union of Lublin on many points.
The Polish nobility therefore viewed the statutes of Lithuania as unconstitutional, because at the signing of Union of Lublin it was said that no law could conflict with the law of Union. The Statutes, however, declared the laws of the Union that conflicted with them to be unconstitutional. Statutes of Lithuania were also used in territories of Lithuania annexed by Poland shortly before Union of Lublin. These conflicts between statutory schemes in Lithuania and Poland persisted for many years.
In culture and language, however, Polish eventually became a dominant one for all of nobility, including the nobility of Ruthenia and Lithuania, replacing the previous Ruthenian. However farmers, town dwellers and other people continued to speak in their own languages, which eventually created a significant rift between the lower social classes of people and the nobility in the Lithuanian and Ruthenian areas of the Commonwealth.
The Union of Lublin was superceded by the Constitution of the Third May from 1791, when the federative Commonwealth was to be transformed into a unitary state by King Stanislaw August Poniatowski. However the constitution was not fully implemented, as the Partitions of Poland (and Lithuania) by Russia, Prussia and Austria-Hungary in 1795 destroyed the Commonwealth. The Union of Lublin was also temporary not active while Union of Kėdainiai was working.
The Union of Lublin created the largest state in Europe's history (if counting only states which are fully in Europe, i.e. not counting the Russian Empire), before the arrival of the European Union in the 20th century. Many historians also consider the Union of Lublin to have created a similar state to the present-day European Union, thus considering the Union to be kind of a predecessor of the Maastricht treaty. The former, however, created a state of countries more deeply linked than the present-day EU.