Editing Sigismund II Augustus (section)

===Union of Lublin===
{{main|Polish-Lithuanian union|Union of Lublin|Polonisation}}
Sigismund's most striking legacy may have been the [[Union of Lublin]], which united Poland and Lithuania into one state, the [[Polish–Lithuanian Commonwealth]], jointly with German-speaking [[Royal Prussia]] and Prussian cities. This achievement might well have been impossible without the monarch's personal approach to politics and ability to mediate.<ref name="EB1911">{{EB1911|inline=1 |last=Bain |first=Robert Nisbet  |author-link=Robert Nisbet Bain  |wstitle=Sigismund II. |volume=25 |page=68}}</ref>

At first, the treaty was perceived as a threat to Lithuanian sovereignty. Lithuanian [[magnates]] were afraid of losing their powers, since the proposed union would lower their rank and status to an equivalent with [[petty nobility]] rather than wealthier Polish aristocracy. On the other hand, the unification would provide a strong alliance against Russian (Muscovite) attack from the east. Lithuania was ravaged by the [[Muscovite-Lithuanian Wars]] which endured for over 150 years. During the [[Muscovite-Lithuanian Wars#Second war (1500–1503)|Second War]], Lithuania lost {{convert|210000|sqmi|km2}} of its territory to Russia, and the final defeat in the [[Livonian War]] would result in the country's incorporation into the [[Tsardom of Russia|Russian Tsardom]]. Furthermore, the [[Polish people|Poles]] were reluctant to aid Lithuania without a ''[[quid pro quo]]''. The most vocal opponent of the union was Sigismund's brother-in-law, [[Mikołaj "the Red" Radziwiłł]] ({{langx|lt|Radvila Rudasis}}), who viewed the agreement as "peaceful [[annexation]] of Lithuania" by Poland. He also resisted [[polonisation]] policies which forced ethnic [[Lithuanians]] to change their names and native language to [[Polish language|Polish]] or [[Latin language|Latin]].

As another war with Russia loomed, Sigismund Augustus pressed the members of parliament (Sejm) for the union, gradually gaining more followers due to his persuasive abilities and auspicious diplomacy. The potential union agreement would lead to the eviction of Lithuanian landowners who opposed the transition of territory from multi-ethnic Lithuania to Poland. Such terms were causing an outrage among the most renowned members of Lithuanian upper classes, but Sigismund was decisive and ruthless in this matter. Moreover, the [[Union of Krewo|personal union]] between the two countries created by the marriage of [[Jadwiga of Poland|Jadwiga]] with [[Jogaila]] in 1385 was not entirely constitutional. Being the last male member of the Jagiellons, childless Sigismund sought to preserve his dynasty's legacy. The newly proposed constitutional union would create one large Commonwealth state, with one [[elective monarchy in Poland|elected monarch]] who would simultaneously reign over both domains.

[[File:Sigismund II August of Poland during Lublin Union in 1569.png|thumb|[[Union of Lublin]]; Sigismund stands in the center holding a [[crucifix]] among nobles, envoys and the [[clergy]].]]

The initial Sejm negotiations on unity in January 1569, near the Polish city of [[Lublin]], were futile. The right of Poles to settle and own land in the Grand Duchy was questioned by Lithuanian envoys. Following Mikołaj Radziwiłł's departure from Lublin on 1 March 1569, Sigismund announced the incorporation of then-Lithuanian [[Podlachia]], [[Volhynia]], [[Podolia]] and [[Kiev]] provinces into Poland, with strong approval from the local [[Ukrainians|Ruthenian]] (Ukrainian) [[gentry]]. Those historic regions, which once belonged to the [[Kievan Rus']], were disputed between Lithuania and Russia. However, the Ruthenian nobles were eager to capitalise on the political or economic potential offered by the Polish sphere and agreed to the terms. Previously, the [[Kingdom of Ruthenia]] or "Ukraine" was abolished in 1349, after Poland and Lithuania split modern-day Ukraine in the aftermath of the [[Galicia–Volhynia Wars]]. Now, under the Union of Lublin, all Ukrainian and Ruthenian territories which were alien in culture, customs, religion and language to the Polish people would be annexed by Catholic Poland. Strong [[westernisation]] and polonisation would follow, including the clandestine suppression of the Ukrainian [[Eastern Orthodox Church]] by future King [[Sigismund III]]. Ruthenia remained under Polish rule until the [[Khmelnytsky Uprising|Cossack uprisings against Polish domination]] and the [[Partitions of Poland]], when Ukraine was annexed by the [[Russian Empire]].

The Lithuanians were compelled to return to the Sejm negotiations under [[Jan Hieronimowicz Chodkiewicz|Jan Hieronim Chodkiewicz]] and continue negotiations. The Polish nobility once again pressed for the full incorporation of the Grand Duchy of Lithuania into Poland, however, the Lithuanians disapproved. The parties eventually agreed on a federal state on 28 June 1569 and on 1 July 1569 the Union of Lublin was signed at [[Lublin Castle]], thus establishing the Polish–Lithuanian Commonwealth. Sigismund Augustus [[ratification|ratified]] the unification act on 4 July, and henceforth governed one of the largest and multicultural countries of 16th-century Europe.