Cossack Hetmanate in the context of "Yurii Khmelnytsky"

The Pereiaslav Agreement or Pereyaslav Agreement (Ukrainian: Переяславська рада, romanized: Pereiaslavska Rada, lit. 'Pereiaslav Council', Russian: Переяславская рада) was an official meeting that convened for a ceremonial pledge of allegiance by Zaporozhian Cossacks to Russian tsar Alexis (r. 1645–1676) in the town of Pereiaslav in central Ukraine, in January 1654. The ceremony took place concurrently with ongoing negotiations that started on the initiative of Hetman Bohdan Khmelnytsky to address the issue of the Cossack Hetmanate with the ongoing Khmelnytsky Uprising against the Polish–Lithuanian Commonwealth and which concluded the Treaty of Pereiaslav (also known as the March Articles). The treaty itself was finalized in Moscow in April 1654 (in March according to the Julian calendar).

Khmelnytsky secured the military protection of the Tsardom of Russia in exchange for allegiance to the tsar. An oath of allegiance to the Russian monarch from the leadership of the Cossack Hetmanate was taken, shortly thereafter followed by other officials, the clergy and the inhabitants of the Hetmanate swearing allegiance. The exact nature of the relationship stipulated by the agreement between the Hetmanate and Russia is a matter of scholarly controversy. The council of Pereiaslav was followed by an exchange of official documents: the March Articles (from the Cossack Hetmanate) and the tsar's declaration (from Russia).

Hetman is a political title from Central and Eastern Europe, historically assigned to military commanders (comparable to a field marshal or imperial marshal in the Holy Roman Empire). First used by the Czechs in Bohemia in the 15th century, it was the title of the second-highest military commander after the king in the Crown of the Kingdom of Poland and the Grand Duchy of Lithuania from the 16th to 18th centuries. Hetman was also the title of the head of the Cossack state in Ukraine after the Khmelnytsky Uprising of 1648. Throughout much of the history of Romania and Moldavia, hetmans were the second-highest army rank. In the modern Czech Republic, the title is used for regional governors.

Zynoviy Bohdan Mykhailovych Khmelnytsky of the Abdank coat of arms (1595 – 6 August 1657) was a Ruthenian nobleman and military commander of Zaporozhian Cossacks as Hetman of the Zaporozhian Host, which was then under the suzerainty of the Polish–Lithuanian Commonwealth. He led the Cossacks to victory in a successful uprising against the Commonwealth and its magnates (1648–1654) that resulted in the creation of an independent Cossack state in Ukraine.

In 1648–1649, the Cossacks under Khmelnytskyi's leadership massacred tens of thousands of Poles and Jews, with more handed over as yasir (slaves) to his Crimean Tatar allies, one of the most traumatic events in Polish and Jewish history. Under his rule of the newly-established Cossack state, the massacres continued until at least 1652. In 1654, Khmelnytsky concluded the Treaty of Pereiaslav with the Russian Tsar and allied the Cossack Hetmanate with Tsardom of Russia, thus placing Ukraine under Russian protection.

The Khmelnytsky Uprising, also known as the Cossack–Polish War, Khmelnytsky insurrection, or the National Liberation War, and Cossack Revolution, was a successful Cossack rebellion with elements of religious war that took place between 1648 and 1657 in the eastern territories of the Polish–Lithuanian Commonwealth, resulting in Cossack victory and the creation of the Cossack Hetmanate in present-day Ukraine. Under the command of Cossack Hetman Bohdan Khmelnytsky, the Zaporozhian Cossacks, allied with the local Ruthenian (Ukrainian) peasantry and initially the Crimean Tatars, fought against the Commonwealth's forces. The war was accompanied by mass atrocities committed by Cossacks against prisoners of war and the civilian population, especially Poles, Jews, Roman Catholic and Ruthenian Uniate clergy, as well as savage reprisals by the Polish szlachta and the loyalist Jeremi Wiśniowiecki, the voivode of Ruthenian descent (military governor) of the Ruthenian Voivodeship.

The uprising has a symbolic meaning in the history of Ukraine's relationship with Poland and Russia. It ended the Polish Catholic szlachta's domination over the Ukrainian Orthodox population; at the same time, it led to the eventual incorporation of eastern Ukraine into the Tsardom of Russia initiated by the 1654 Pereiaslav Agreement, whereby the Cossacks would swear allegiance to the tsar while retaining a wide degree of autonomy. The event triggered a period of political turbulence and infighting in the Hetmanate known as the Ruin. The success of the anti-Polish rebellion, along with internal conflicts in Poland and concurrent invasions waged by Russia and Sweden against the Poles, ended the Polish Golden Age and caused a secular decline of Polish power during the period known as "the Deluge".

The Poltava Regiment (Ukrainian: Полтавський полк) was one of ten territorial-administrative subdivisions of the Cossack Hetmanate. The regiment's capital was the city of Poltava, now in Poltava Oblast of central Ukraine.

The Poltava Regiment was founded in 1648 during the Khmelnytsky Uprising. Following the signing of the Treaty of Zboriv in 1649 it consisted of 19 sotnias, and had 2970 registered cossacks. In 1775, the regiment was officially abolished, and its territory was reformed into the Little Russia Governorate.

Poltava Oblast (Ukrainian: Полтавська область, romanized: Poltavska oblast), also referred to as Poltavshchyna (Ukrainian: Полтавщина), is an oblast (province) of central Ukraine. The administrative center of the oblast is the city of Poltava. Most of its territory was part of the southern regions of the Cossack Hetmanate. Population: 1,352,283 (2022 estimate).

Three other important cities in the oblast are Horishni Plavni, Kremenchuk, and Lubny.

Novorossiya Governorate was an administrative-territorial unit (guberniya) of the Russian Empire, which existed in 1764–1783 and again in 1796–1802. It was created soon after the establishment of the Ukrainian fortification line. The governorate was governed according to the "Plan for the Colonization of New Russia Governorate" issued by the Russian Senate. It became the first region in Russia where Catherine the Great allowed foreign Jews to settle.

Most of its territories belonged to the Zaporozhian Sich as well as the Poltava Regiment and Myrhorod Regiment of the Cossack Hetmanate. Its establishment was strategically successful and advantageous for Russia, and after the conclusion of the Russian war against Turkey in 1774 it gave a way for Russia to access the Black Sea and establish an area that became known as Novorossiya ("New Russia"). It was created based on the Military Frontier of the Austrian Empire against the Ottoman Empire and involved many military units from the region that were resettled in Ukraine. The military units included mounted cossacks (or hussars) and mounted pikers (or lancers).

Samiilo Vasyliovych Velychko (Ukrainian: Самі́йло Васи́льович Вели́чко; 11 February 1670 – after 1728) was a Cossack nobleman and chronicler who wrote the first systematic presentation of the history of the Cossack Hetmanate.

Sumy Oblast (Ukrainian: Сумська область, romanized: Sumska oblast), also known as Sumshchyna (Сумщина), is an oblast (province) in northeast Ukraine. The oblast was created in its modern-day form, from the merging of raions from Kharkiv Oblast, Chernihiv Oblast, and Poltava Oblast in 1939 by the Presidium of the Supreme Soviet of the Soviet Union. The estimated population is 1,035,772 (2022 estimate).

The administrative center of the oblast is the city of Sumy. Other important cities within the oblast include Konotop, Okhtyrka, Romny, and Shostka. The modern region combines territories of the historical Severia (northern part) and Sloboda Ukraine (southern part). On territory of the Sumy Oblast important centers of Ukrainian culture are located, such as the city of Hlukhiv which served as a hetman residence during the Cossack Hetmanate as well as the cities of Okhtyrka and Sumy which were regional centers of the Sloboda Ukraine.