Cossacks in the context of "Irregular military"

Between 1441 and 1774, the Crimean Khanate and the Nogai Horde conducted slave raids throughout lands primarily controlled by Russia and Poland–Lithuania. Concentrated in Eastern Europe, but also stretching to the Caucasus and parts of Central Europe, these raids were often supported by the Ottoman Empire and involved the transportation of European men, women, and children to the Muslim world, where they were put on the market and sold as part of the Crimean slave trade and the Ottoman slave trade. The regular abductions of people over the course of numerous incursions by the Crimeans and the Nogais greatly drained Eastern Europe's human and economic resources, consequently playing an important role in the emergence of the semi-militarized Cossacks, who organized retaliatory campaigns against the raiders and their Ottoman backers.

Trading posts in Crimea had previously been established by the Genoese and the Venetians to facilitate earlier Western European slave routes. The Crimean–Nogai raids largely targeted the "Wild Fields" of the Pontic–Caspian steppe, which extends about 800 kilometres (500 mi) north of the Black Sea and which now contains the majority of the combined population of southeastern Ukraine and southwestern Russia.

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).

Kharkiv is the second-largest city in Ukraine. Located in the northeast of the country, it is the largest city of the historic region of Sloboda Ukraine. Kharkiv is the administrative center of Kharkiv Oblast and Kharkiv Raion. Prior to the Russian invasion of Ukraine in early 2022, it had an estimated population of 1,421,125.

Founded in 1654 as a Cossack fortress, by late 19th century Kharkiv had developed within the Russian Empire as a major commercial and industrial center. From December 1919 to January 1934, Kharkiv was the capital of the Ukrainian Soviet Socialist Republic. During this period migration from the distressed countryside and a relaxation of restrictions on Ukrainian cultural expression changed the city's ethnic complexion: Ukrainian replaced Russian as the largest recorded nationality. It was the sixth largest city in the Soviet Union during its existence.

Dnipro is Ukraine's fourth-largest city, with about one million inhabitants. It is located in the eastern part of Ukraine, 391 km (243 mi) southeast of the Ukrainian capital Kyiv on the Dnipro River, from which it takes its name. Dnipro is the administrative centre of Dnipropetrovsk Oblast. It hosts the administration of Dnipro urban hromada. Dnipro has a population of 968,502 (2022 estimate).

Archeological evidence suggests the site of the present city was settled by Cossack communities from at least 1524. Yekaterinoslav ("glory of Catherine") was established by decree of the Russian Empress Catherine the Great in 1787 as the administrative center of Novorossiya. From the end of the 19th century, the town attracted foreign capital and an international, multi-ethnic workforce exploiting Kryvbas iron ore and Donbas coal.

The Caucasian War (Russian: Кавказская война, romanized: Kavkazskaya voyna) or the Caucasus War was a 19th-century military conflict between the Russian Empire and various peoples of the North Caucasus who resisted subjugation during the Russian conquest of the Caucasus. It consisted of a series of military actions waged by the Russian Imperial Army and Cossack settlers against the native inhabitants such as the Adyghe, Abazins, Ubykhs, Chechens, and Dagestanis as the Tsars sought to expand.

Russian control of the Georgian Military Road in the center divided the Caucasian War into the Russo-Circassian War in the west and the conquest of Chechnya and Dagestan in the east. Other territories of the Caucasus (comprising contemporary eastern Georgia, southern Dagestan, Armenia and Azerbaijan) were incorporated into the Russian Empire at various times in the 19th century as a result of Russian wars with Persia. The remaining part, western Georgia, was taken by the Russians from the Ottomans during the same period.

The Cossack raids largely developed as a reaction to the Crimean–Nogai slave raids in Eastern Europe, which began in 1441 and lasted until 1774. From c. 1492 onwards, the Cossacks (the Zaporozhian Cossacks of southern Ukraine and the Don Cossacks of southern Russia) conducted regular military offensives into the lands of the Crimean Khanate, the Nogai Horde, and the Ottoman Empire, where they would free enslaved Christians and return home with a significant amount of plunder and Muslim slaves. Unlike the Tatars, Cossack raiders were capable of capturing and devastating highly fortified cities. Though difficult to calculate, the level of devastation caused by the Cossack raids is roughly estimated to have been on par with that of the Crimean–Nogai slave raids. According to History of Ruthenians, Cossack raids during Sirko's era were a hundred times more devastating than Crimean–Nogai raids.

The Zaporozhian Cossacks or Zaporizhian Cossacks, also known as the Zaporozhian Cossack Army or the Zaporozhian Host (Ukrainian: Військо Запорозьке, romanized: Viisko Zaporozke), were Cossacks who lived beyond (that is, downstream from) the Dnieper Rapids. They were predominantly Ruthenians, but also included other ethnic groups (most notably their legendary Kosh Otaman Ivan Sirko was of Moldavian origin). Along with Registered Cossacks and Sloboda Cossacks, Zaporozhian Cossacks played an important role in the history of Ukraine and the ethnogenesis of Ukrainians.

The Zaporozhian Sich grew rapidly in the 15th century from serfs fleeing the more controlled parts of the Polish–Lithuanian Commonwealth. The least controlled region, that was located between the Dniester and mid-Volga was first known from the 15th century as the Wild Fields, which was subject to colonization by the Zaporozhian Cossacks. Zaporozhian Host became established as a well-respected political entity with a parliamentary system of government. During the course of the 16th, 17th and well into the 18th century, the Zaporozhian Cossacks were a strong political and military force that challenged the authority of the Polish–Lithuanian Commonwealth, the Tsardom of Russia, and the Crimean Khanate.

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 Russian conquest of Siberia took place during 1581–1778, when the Khanate of Sibir became a loose political structure of vassalages that were being undermined by the activities of Russian explorers. Although outnumbered, the Russians pressured the various family-based tribes into changing their loyalties and establishing distant forts from which they conducted raids. It is traditionally considered that Yermak Timofeyevich's campaign against the Siberian Khanate began in 1581. The annexation of Siberia and the Far East to Russia was resisted by local residents and took place against the backdrop of fierce battles between the indigenous peoples of Siberia and the Russian Cossacks, who often committed atrocities against indigenous Siberians. The conquest of the region was a spontaneous event organized by a group of adventurers; it is one of the early European colonial campaigns.