Editing Sigismund II Augustus (section)

===Livonia===
{{main|Old Livonia|Duchy of Livonia|Livonian War}}
[[File:Steven van Herwijck, Sigismund II Augustus, 1520-1572, King of Poland 1548 (obverse), c. 1562, NGA 45436.jpg|thumb|left|200px|Medal obverse featuring Sigismund from 1562, [[National Gallery of Art]] in [[Washington, D.C.]]]]
During Sigismund Augustus' reign, Livonia was in political turmoil. His father, Sigismund I, permitted [[Albert, Duke of Prussia|Albert of Prussia]] to introduce the Protestant [[Reformation]] and secularize the southern part of the [[Teutonic Order State]]. Albert then established Europe's first Protestant state in the [[Duchy of Prussia]] in 1525, but under [[Treaty of Cracow|Polish suzerainty]]. However, his efforts to introduce Protestantism to the [[Livonian Brothers of the Sword]] in the northernmost part of the region was met with fierce resistance and divided the [[Livonian Confederation]]. When Albert's brother [[Wilhelm von Brandenburg|Wilhelm]] and [[Archbishopric of Riga|Archbishop of Riga]] attempted to implement a [[Church Order (Lutheran)|Lutheran church order]] in his [[diocese]], the [[Roman Catholic Church|Catholic]] estates rebelled and arrested both Wilhelm and his [[Coadjutor bishop|bishop coadjutor]], [[Christopher, Duke of Mecklenburg]].

As Prussia was a tributary state of the Polish Crown, Sigismund Augustus, a Catholic, was forced to intervene in favour of Protestant Albert and his brother Wilhelm. In July 1557 the Polish forces left for Livonia. The armed intervention proved to be successful; the Catholic Livonians surrendered and signed the [[Treaty of Pozvol]] on 14 September 1557. The agreement placed most Livonian territories under Polish protection and ''[[de facto]]'' became part of Poland. [[Gotthard Kettler]], the last Master of the Order, was granted the newly established [[Duchy of Courland and Semigallia]]. Wilhelm was restored to his former position as archbishop on Sigismund's demand, with the Lutheran church order being enacted.

The incorporation of Courland into the Polish sphere of influence created an alliance which threatened Russia's plans of expanding into the [[Baltic coast]]. Sigismund directed the alliance against [[Ivan the Terrible]] to protect lucrative trade routes in Livonia, thus creating a new valid ''[[casus belli]]'' against the [[Tsardom of Russia|Russian Tsardom]]. On 22 January 1558, Ivan invaded the Baltic states and started the [[Livonian War]], which lasted 25 years until 1583. Russia's eventual defeat in the war legally partitioned Livonia between Poland ([[Latvia]], southern [[Estonia]]) and [[Sweden]] (central-northern Estonia). The Polish sector became subsequently known as [[Duchy of Livonia|Polish Livonia]] or ''Inflanty''; it was settled with colonists from Poland proper resulting in systematic [[polonisation]] of these lands.