(Cambridge Concise Histories) Jerzy Lukowski, Hubert Zawadzki - A Concise History of Poland-Cambridge University Press (2006)

Sigismund II Augustus felt that only a new Union, on terms acceptable to both the Crown and Lithuania, would give the nobility of both a real stake in the survival of a reconstructed polity. The outright annexationism of the Executionists would not do. Convergence of a kind had long been under way. The Polish written and spoken word was, by the late fifteenth century, making rapid progress among Lithuania’s elites, to produce a fascinating written and spoken linguistic hybrid of Belarusian, Lithuanian, Latin and Polish. By the 1560s, if not earlier, the Lithuanian nobility at all levels were predominantly Polish speakers and Lithuanian itself had been reduced to the language of the peasantry. Cultural polonization was certainly not opposed by Lithuanian elites: many, not least Rus’ Orthodox, positively embraced it as a channel to a more sophisticated western European culture. The Radziwills’ conversion to and enthusiastic patronage of Calvinism was a means of combining integration with distinctiveness. But political polonization was a very different matter. The importation of distinct Polish-style courts, sejmiki and genuine elections to a central Sejm and to local offices threatened to overturn the patrimonial dominance of the members of the hospodafs council. The resumption of grand-ducal domain threatened them with economic catastrophe. But irresistible pressures were building up. The constant presence during the Muscovite wars of Polish troops, drawn mainly from the szlachta, served to familiarize their Lithuanian counterparts with Polish ideas and institutions. Sigismund Augustus’ Privilege of Vilnius of July 1563 aimed to win round Orthodox nobles by restoring their access to offices on the hospo-dar's council. The Lithuanian magnates, led by the Radziwills, offered concessions. The Vilnius Sejm of November 1 565 to March 1566 sanctioned the introduction of distinct elective courts on the Polish model. A hierarchy of local officials patterned on Poland’s followed in 1566 as part of a new codification of common law (the so-called Second Lithuanian Statute). The Lithuanian Sejm, hitherto largely a magnate mouthpiece, formally assumed the same legislative powers and procedures as the Crown’s. Union was being administratively engineered from within.

The climax came at the Sejm which met in Lublin in January 1569. Sigismund insisted that the Lithuanian lords and envoys should attend. Prompted by Sigismund, the Poles declared their readiness to accept a separate hierarchy of great offices of state for Lithuania - but there would have to be a common Sejm; the Poles’ right to settle and own land in the Grand Duchy would have to be conceded. This last demand led to fears that the generally wealthier Poles would swamp the Grand Duchy. When most of the Lithuanian representation walked out on 1 March, Sigismund angrily announced the incorporation of Volhynia and Podlasie, part of Lithuania’s Rus’ lands, into the Crown. The local boyars, comparatively few by the standards of the Polish lands proper - at most they may have accounted for some 3 per cent of the population of these territories - complied with little fuss. As far as most of them were concerned, it was their obligation to follow the dictates of their hospodar, Sigismund, heir to the rulers of old Rus’ - a ruler, moreover, who had only recently lifted the restrictions imposed by Lithuanian Catholic Vilnius on Orthodox subjects’ access to the great offices of state; incorporation into the Crown brought the promise of sharing in Polish-style rights, liberties and freedoms.

On 16 March, the king ordered the senators and envoys from Royal Prussia, attending as observers, to take their seats in the assembly - their separate status, too, would end. They caved in. On 6 June, the royal chancellery announced the incorporation into the Crown of the sprawling palatinate of Kiev, with the overwhelming approval of the local nobility. If the Lithuanian objectors persisted, there was every likelihood that the original annexationist demands of the Executionists would be carried. Sigismund still believed that ‘voluntary’ union was better: he even promised that the resumption of royal demesne would not apply to Lithuania ( in fact, it did not even apply to the former parts of the Grand Duchy which were incorporated into Poland). The Poles agreed that Lithuanians could enjoy reciprocal rights of settlement in the Crown. On 28 June the last objections were overcome. The new Union was confirmed by the king 011 4 July. A new entity, the Rzeczpospolita Obojga Narodow, Polskiego i Litewskiego, ‘The Commonwealth of the Two Nations, the Polish and Lithuanian’, had come into being.