Swedish Lithuania

Swedish Lithuania, officially known as the Grand Duchy of Lithuania (Swedish: Storfurstendömet Litauen, Latin: Magnus Ducatus Lituaniæ), was a dominium directum protectorate of the Swedish Empire under the rule of King Charles X Gustav in accordance with the Union of Kėdainiai. It de jure existed from 1655 until 1657 when it was terminated and fully reincorporated into the Polish–Lithuanian Commonwealth.

Swedish occupation
In 1654, the Tsardom of Russia launched its invasion against the Polish–Lithuanian Commonwealth, which resulted in huge swathes of the territory falling into the hands of the Russian army. Noting the weak military performance of the Commonwealth, the Swedish Empire sought to take advantage of the political turmoil and occupy parts of the Polish–Lithuanian state: Sweden wanted to make Lithuania a permanent part of its imperial domain as the territory was strategically important in securing the Baltic Sea from Russia. In the summer of 1655, the Swedish army invaded Western Poland and began threatening to do the same to Lithuania. After learning about King John II Casimir fleeing the country, Lithuanian magnate Janusz Radziwiłł and other members of the Lithuanian nobility began considering negotiations with Sweden. This decision was also influenced by separatist religious motives as it was strongly supported by the Lithuanian Protestant elite. After Sweden's occupation of northwestern Lithuania, commander Zygmunt Przyjemski informed King Charles X Gustav that Poland is willing to formally cede Lithuania to Sweden in exchange for peace — this proposal was rejected.

Treaty of Kėdainiai
On 17 August 1655, the Treaty of Kėdainiai was signed by Jonušas Radvila and other 400 pro-Swedish signatories. The treaty laid out certain conditions — the Lithuanian nobility wanted Sweden to protect Lithuania from Moscow, guarantee the country's neutrality in the conflict, political and religious freedoms. These conditions were rejected as they also vaguely mentioned Lithuania having the right to leave Sweden. The Swedish also avoided directly participating in the conflict with the Tsardom of Russia because, in reality, they didn’t have enough manpower in Swedish Livonia to properly assist Lithuania in case of need. Despite this, Sweden promised Lithuania that it would help them in reclaiming their lost territory.

Union of Kėdainiai
On 20 October 1655, over 1,000 nobles, mostly from Samogitia, gathered at the Kėdainiai Manor, signed the Union of Kėdainiai on behalf of the Grand Duchy of Lithuania, dissolved the Polish–Lithuanian Commonwealth and solemnly declared the establishment of a personal union with the Swedish Empire. The Swedish side was represented by Lord High Treasurer Magnus Gabriel De la Gardie and Governor Bengt Skytte, with the latter also holding the position of viceroy. King of Sweden Charles X Gustav became Grand Duke of Lithuania. Following this, another act was signed by which the Lithuanian nobility pledged its loyalty to the Swedish Crown. On 23 October 1655, the Lithuanian Advisory Council was inaugurated. Swedish Lithuania was set up as a dominicum directum with Jonušas Radvila being promised exceptional rights to certain estates. It is known that both Jonušas and Boguslavas Radvila (Bogusław Radziwiłł) initially wanted to acquire the Lithuanian territories of Minsk, Navahrudak, Brest Voivodeships and Volkovysk, Grodno Counties, as well as the Polish Podlaskie Voivodeship. Meanwhile, ethnic Lithuania was supposed to remain under the direct rule of Sweden. Jonušas Radvila also hoped to become an uncrowned ruler of the entire Swedish protectorate, but his endeavour was unsuccessful.

Seeking to improve Sweden’s reputation among the Lithuanian peasantry and secure a greater political advantage over the Lithuanian nobility, Gabriel De la Gardie was entrusted with assuring them the abolition of serfdom. However, this ultimately did not help to improve their relations with the peasantry as they were left with the burden of supplying significant resources to the Swedish forces and their military effort. The Swedish administration began confiscating estates from nobles who did not recognise their authority and set the tax rate to 110 000 thaler — many who refused or were unable to pay them were killed, arrested or deported to Sweden with their property being destroyed.

Disestablishment
As time passed, some layers of society, namely the minor nobility and peasantry, began to withdraw their support for Swedish rule. This was mostly a consequence of the Swedish administration introducing heavy taxation and its unability to control the brutality of its own army in the region. In the spring of 1656, certain segments of nobility in Lithuania began revolting against the Swedish, which was followed by the Polish decisive victory against the Swedish Empire in the Battle of Prostki. In 1657, the remaining Swedish troops stationed in the Biržai Castle were ousted and Swedish Lithuania disintegrated. Following this, Boguslavas Radvila, who had served as the acting Grand Hetman of Lithuania and the commander of Swedish forces against Poland, faced trial and was exiled to Königsberg.