Avigdor Levy identified a number of instances where, from the late 1700s various newly arrived 'Cossack' refugees arrived within the Ottoman Empire, to resettle and were employed in various military auxiliary roles [1].
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[1] Levy, Avigdor. "Formalization of Cossack Service Under Ottoman Rule." East Central European Society and War. Ed. Gunther E. Rothenberg et al. New York: Columbia University Press, 1982: 491-505.
In 1826, the 'Silistra Cavalry Regiment' was formed, as part of the general reorganization of that year, and was raised in Silistria province (the Danube Delta), and made up of Turks, Tatars and Christians in equal proportions.
The Regiment-Brigade was organised into two ‘alays’ (regiments):
In terms of the uniform of the 1826 regiment, the men were issued with:
The first Ottoman Cossack Regiment/Brigade, can be dated back to 1848 [1].
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[1] Marcel Roubicek (1978) Modern Ottoman Troops, 1797-1915: In Contemporary Pictures. Franciscan Printing Press: 13.
[2] Egyptian Circassians (formed as a cavalry auxiliary unit in the Egypt Army in the 1840s). Nevertheless, would still be representative of the type of uniforms worn by the 1848-1853 1st Regiment.
The 1854 banner of the Ottoman Cossacks regiment, was received in Edirne when the Cossacks officially took an oath to join the Sultan’s service, This was the old banner of Zaporozhian Cossacks (which had been kept in Constantinople, following the Ottoman-Russian war in 1828-29).
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[1] Finally, there is a 2009 Wikimedia Commons version of the "Banner of the Polish Sultan Cossacks Division during Crimean War", which is red, and shows a crescent and polish eagle, but this has no historical verification.
Right - Czajkowski, is pictured here in the uniform of the General commanding the 'Ottoman Cossack Brigade'. Michal Czajkowski, or Sadyk Pasha (his Turkish name) was born 19 September 1804 in Halchyn, near the town of Berdychiv in the Province of Volhynia, which had been annexed to the Russian Empire at the end of the eighteenth century.
Left - The 1853-Crimean War uniforms of an officer, and soldier in the Ottoman Cossack Brigade. In autumn of 1855, the brigade Had about 2,000 troops in the pay of the British, and were commanded by General Wladyslaw Zamoyski (a Brigadier General of the Turkish army of British origin), as well as being organised by Czajkowski.
Right - An example of the Paris National Guard buckle plate, used by the officers of the 1st Cossack Regiment.
Below - Outline of the 1st Cossack regiment's history and uniform, and the later 1856 Cossack brigage (David Cliff 1997 Polish Volunteers with the Turkish Army. The War Correspondent. Volume 14 No.4, January):
Right - An example of a Chasseurs à cheval modèle 1854 Dolman for Officers, adopted by the 2nd Cossack Regiment.
Below - Outline of the 2nd Cossack regiment's history and uniform (David Cliff 1997 Polish Volunteers with the Turkish Army. The War Correspondent. Volume 14 No.4, January):
Right - The 'Circassian' cavalry uniform, adopted by the 3rd Cossack Regiment, this is illustrated in Mahmud Sevket Pasa ‘L'Organisation et les Uniformes de l'Armee Ottomanne' (1907).
Below - Outline of the 3rd Cossack regiment's history and uniform (David Cliff 1997 Polish Volunteers with the Turkish Army. The War Correspondent. Volume 14 No.4, January):
Left - This painting from 1944, published in 'Polish Armed Forces Through the Ages' (London, 1944 W.Dziewanowski, & A. Minkiewicz), actually confuses the later 1861-1876 1st Ottoman Cossack Regiment's uniform (shown with gold lace - which should be silver), with the correct uniform for the Crimean War period worn by the same regiment.