Of the different branches of Cossacks, the only one that documentably would allow Jews into their society were the Cossacks of Ukraine. When Poland and Lithuania were merged by Polish King Sigismund Augustus into one commonwealth (in Union of Lublin, 1569), the provinces of Volhynia, Podilia, and the rest of Ukraine were separated from Grand Duchy of Lithuania and came under the direct rule of Poland.
About that time an island fortress of Khortytsia was established in the river Dnieper, and Cossacks were stationed there for protection against the invasions of the Crimean Tatars. This fortress with its garrison became known as the "Zaporozhian Sich" (meaning "the fortified camp beyond the rapids"). These Cossacks were eventually joined by Ruthenian poor nobility, boyars, foreign mercenaries and townsfolk , runaway serfs, escapees from the Ottoman territories, and adventurers. A town grew around Khortytsia, and many traders (Jews among them) settled there.
Cossack society was ethnically diverse (some Cossacks may have had their origins as far as in Scotland ). Jews also served in the ranks of the Cossacks, although the mechanism of their entry into the Cossack ranks is unclear. The Cossack regiments in Ukraine served administrative purposes, aside from military, and had constant demand for able administrators, educated diplomats, scribes. Jews could fulfill those tasks, because of their level of literacy and natural command of several languages. Although the Cossacks were not known for religiosity before the 17th century it is presumed that conversion was a requirement for promotion in the Cossack ranks by early 1600s. In 1681 Ahmad Kalga, chief councilor of the Khan of Crimea, complained to the Polish ambassador, Piasaczinski, that the Cossacks of the Lower Dnieper had attacked Crimea. Piasaczinski replied that the Cossacks were not subjects of the king of Poland, and that he therefore could not be held responsible for the "acts of uncontrollable rovers of the desert that were apostates from all faiths, Poles, Muscovites, Wallachians, Turks, Tatars, Jews, etc., among them".
The responsa of Joel Särkes discusses "Berakha the Hero", who fought in the ranks of the Cossacks and fell in battle against the Muscovites. The deposition of Berakha's fellow-cossack "Joseph son of Moses" in the rabbinical court-case of Berakha's widow's permission to remarry states that there were at least 11 Jews in the cossack ranks of the Nalyvayko army in the battle in whick Berakha was killed. In 1637 Ilyash (Elijah) Karaimovich was one of the officers of the registered Cossacks, and became their "starosta" (elder) after the execution of Pavlyuk. Karaimovich is presumed to be born a Karaim (a Turkic ethnic group adherent to Karaite Judaism.)
In the 1930s a cache of large number of documents written in Hebrew was found by the historian and linguist Saul Borovoy in the archives of the Zaporozhian Sich that were kept at the State Archive in Moscow since the razing of the Sich by the General Tekeli in 1775. The documents dealt with foreign and fiscal policies of the Sich, and evidenced not only the presence of (presumably converted) Jews in the upper stratum of the Cossack society (at least 4 are mentioned by name in the Borovoy dissertation), but also in the regiments as well.
The Sich Archive became the basis of Borovoy's 1940 tripartite doctoral dissertation. Parts I and II were published in 1940 in Leningrad and 1941 in Moscow respectively. Borovoy could not return to this subject in the post-War anti-semitic climate in Soviet Union, and the 3rd part of his dissertation was never printed and the typographic 'formes' already assembled were destroyed. Borovoy's articles on the subject first came under attack from the anti-semitic circles in Soviet academia, because his research refuted the label of cowardice and timidity commonly applied to the Jews by the anti-semites. Later Borovoy was criticized by those Jewish circles unwilling to admit the class-related antagonism that made possible Jewish presence on the Cossacks' side.
In the ancient epics known as dumy sung by the Ukrainian kobzari there is a reference made to a colonel named Matviy Borokhovych (1647), who, as his family name (meaning "son of Baruch") indicates Jewish origin.
Cossack surnames of Jewish origin
Cossack families of Jewish origin include Hertzyk, Osypov-Perekhrest, Perekhryst, Kryzhanovsky, Markevych/Markovych, Zhydok, Zhydovynov, Leibenko, Yudin, Yudaev, Khalayev, Nivrochenko, Matsunenko, Shabatny, Zhydchenkov, Shafarevich, Marivchuk, Magerovsky and others.
Changes of sentiment during the 17th century
The Zaporozhian Cossacks were generally indifferent to religious matters and bore no particular ill will toward the Jews up to the time of Hetman Nalyvaiko,. They often included Jews among their company, but the demographic changes caused by the Mazur immigration introduced a negative feeling against the Jews from Poland to Ukraine during the reign of Sigismund III (1587-1632). The guilds that were established, which always feared the competition of the Jews, played a prominent part in connection with various accusations. The higher nobility, however, depended largely on the Jews to act as their leaseholders, agents, and financial managers, and this served in a significant measure as a bar to persecution.
The Israilovsky Regiment
In December 1787, Prince Potemkin, Catherine the Great's consort and co-ruler, founded a regiment of Jewish Cossacks for the purpose of liberating Jerusalem -- the culmination of his philo-Semitism .
The first partition of Poland in 1772 brought large numbers of Jews into the Russian empire. Catherine granted Potemkin a huge estate, named Krichev, in the newly acquired lands. Potemkin thus came into contact with Jews for the first time. Potemkin was embarking on the task of populating the empty southern steppes around the Black Sea with settlers, and he immediately tried to attract Jews from both Poland and the Mediterranean to his new settlements, in particular those Jews that were active in viticulture. He resettled these Jews in empty smallholdings left by the Zaporozhians. He also gathered around him a coterie of rabbis with whom he would discuss theology.
One in particular, Joshua Zeitlin, a wealthy merchant and scholar, became his close friend. "The two men - consort of the Russian Empress and rabbi in yamulka and ringlets - would ride together chatting amicably. Zeitlin 'walked with Potemkin like a brother and friend'. He achieved a position that no practising Jew in Russia has ever achieved before or since, remaining proudly unassimilated, steeped in rabbinical learning and piety, yet standing high in the Prince's court. Potemkin promoted Zeitlin to 'court counsellor' with a title of nobility. Russian Jews called him 'HaSar Zeitlin' (lord Zeitlin) ."
After discussions with Zeitlin and his perambulant rabbis about the fighting prowess of the Biblical Israelites, the Prince decided to arm the Jews. Potemkin had raised a Jewish cavalry squadron on his estate, and when the Russo-Turkish war started, he wanted to liberate Constantinople for the Orthodox Church; he supported the idea of helping the Jews liberate Jerusalem. Then Potemkin founded the Israelovsky Regiment of Jewish Cossacks. The Jewish Cossacks were commanded by a German, Prince Ferdinand of Braunsweig. The Prince de Ligne, doyen of 18th-century cosmopolitanism and a philo-- Semite wrote: 'Prince Potemkin formed the singular project of raising a regiment of Jews,' he wrote to his master, the Habsburg emperor Joseph II. 'He intends to make Cossacks of them. Nothing amused me more .'
Soon two squadrons of Jewish Cossacks were on patrol against the Turks, but Ligne claimed that they were not a success. After seven months' training, he sadly decided to end his rare experiment.
This matter remains controversial, since no documents to corroborate the Potemkin regiment are present in the State Military Archive in Moscow.
It has been suggested  that some of the Jewish Cossacks followed Colonel Berek Joselewicz and joined Napoleon's Polish cavalry formations. Joselewicz was killed in a night ambush by the Hungarians during Napoleon's 1809 campaign. It has been suggested  that there were veterans of the Potemkin's regiment fighting for the Emperor at some of his most celebrated victories.
Jewish Polish Cossacks
The great Polish poet Adam Mickiewicz (who was a descendant of a Frankist family (i.e. of a follower of Jakob Frank)) helped form another regiment of Jewish Cossacks - Hussars of Israel - to fight against the Russian Empire, alongside Britain, France and Turkey, in the Crimean war. These lancers fought alongside dissident Cossacks against the Russians outside Sevastopol.
Civil War in Russia
During the Civil War (1918-1920) that ensued after the Russian Revolution of 1917 many Jews served in the "Red Cossacks" (Красное Казачество), cavalry regiments of the Red Army. One such regiment in the Kotovsky Brigade was commanded by the anarchist Sholom Schwartzbard.
- ↑ ("Akty Yuzhnoi i Zapadnoi Rossii," ii. 148)
- ↑ Володимир ГОЛОБУЦЬКИЙ. ЗАПОРОЗЬКЕ КОЗАЦТВО. КИЇВ — 1994, Віталій ЩЕРБАК. УКРАЇНСЬКЕ КОЗАЦТВО: формування соціального стану. Друга половина XV — середина XVII ст. КИЇВ — 2000
Maxym Kryvonis may have been a mercenary soldier from Scottland. Ivan Pidkova was from Moldavia.
- ↑ Боровий С. А. Євреї в Запорозькій Ciчi. //Праці Інституту єврейської культури ВУАН. - К., 1930.
- ↑ (Kostomarov, l.c. p. 55)
- ↑ (1601; Harkavy, "Yevrei-Kazaki," in "Russki Yevrei," 1880, p. 348; from Responsa Bayit Chadash hayeshanot (שו"ת בית חדש הישנות), 57)
- ↑ (Kostomarov, l.c. p. 135
- ↑ Jewish Encyclopedia- Cossacks, Complaint of Cossack Depredations
- ↑ Мішалов М. Українські кобзарські думи. До питання виникнення розвитку та сучасного стану українського кобзарського епосу. — Сідней, 1990 (Ukrainian) Mishalow M. Ukrainian kobzar dumy. Regarding the question of the development and contemporary state of Ukrainian kobzar epos - Sydney, 1990
- ↑ Jewish Encyclopedia - Cossacks, Early Uprisings
- ↑ 11.0 11.1 11.2 11.3 11.4 Simon Sebag Montefiore on Russia's treatment of the Jews -in The Spectator Sep 16, 2000
- Евреи-казаки в начале ХVІІ в. // Киевская старина. – 1890. – № 5. – С. 377-379. In Russian
- Iokhvodova, A. "Jewish Zaporozhians and the Hadjibey Fortress" Vestnik; in Russian
- Borovoy, S. «Евреи в Запорожской Сечи (по материалам сечевого архива)» («Исторический сборник», Л., 1934, т. 1); in Russian
- Kostomarov, M. Ruina, istoricheskaia monografiia iz zhizni Malorossii 1663–1687 gg. (The Ruin: A Historical Monograph on the Life of Little Russia from 1663 to 1687, 1st edn in Vestnik Evropy, nos 4–9  and nos 7–9 ),
- Schreiber, M. The Shenhold Jewish encyclopedia (3rd edition), N.Y. 2002
- Dr. Serhii Plokhy. The Cossacks and Religion in Early Modern Ukraine. Oxford University Press 2001
- Jewish Encyclopedia - Cossacks
- Jewish Zaporozhians (in Russian)
- Montefiore, Simon Sebag "Kosher cossacks". The Spectator. Sep 9, 2000
- Kosher Cossacks
- Головний Apxiв давніх актів у Варшаві. - Ф. «Apxiв Замойських». - № 3048. - p.286.: «Mycyk J. Zyd na Siczi Zaporoskej w XVII w. // Biulatyn Zudowskego Instytutu Istorycznego w Polsce. - Warszawa, 1993. - p. 65-66.
- Horn M. Powinnosci wojenne zydow w Rzeczy Potpolitej w XVI, XVII wieku. - Warszawa, 1978.
- p. 103.
- Luber S. Die Herkunft von Zaporoger Kozaken des 17 Jahrhunderts nach personennamen. Berlin, 1983. - p.100.
- Архив Юго-Западной России. - Киев., 1914. - Ч. III. - Т.4. - № 45. - p.100-102.
- Січинський В. Чужинці про Україну. - К., 1992. - p. 99-100.
- Центральний держащий історичний apxiв України в Києві). - Ф. 229. - On. I. - № 232. - Арк. 199.
- Лиман І. I. Церква в духовному cвіті Запорозького козацтва. - Запоріжжя, 1992. - p.8.
- Скальковський А. О. Історія Нової Ciчi або останнього Коша Запороэького. -Дніпропетровськ, 1994. - p. 192.
- Apxiв Коша Нової Запорозької Ciчi. Опис справ. 1713-1776. - К., 1994. - С. 77.
- Боровий С. А. Євреї в Запорозькій Ciчi. //Праці Інституту єврейської культури ВУАН. - К., 1930.uk:Козаки єврейського походження