The history of the Cossacks spans several centuries.
The origins of the first Cossacks are Slavic, in 1710 Constitution of Pylyp Orlyk confirmed Khazar origin. The Academician Zabelin mentioned that peoples of the prairies and of the woods had always needed "a live frontier", and even ancient Borisphenites and Tanaites could be the predecessors of Cossacks, not only Khazars, which assimilated/included Severians, Goths, Scythians and other ancient inhabitants, as insisted by the Cossack folklore, the Constitution of Pylyp Orlik, and numerous Cossack historians. Because of the need of both the Reds and the anti-Bolshevik forces to deny any Cossack ethnicity, the traditional post-imperial historiography dates the emergence of Cossacks to the 14th-15th centuries. Non-mainstream theories, however, have lent the date 948 from imperial historiography, and ascribed an earlier Cossack existence to the tenth century, but denied Cossack links to both "the old people" (Khazars) and "the new people" (Russians and Ukrainians; the very terms "old people" and "new people" being coined by Metropolitan Ilarion.) specifically mentioning 948 as the year when the inhabitants of the Steppe under the leader named Kasak or Kazak routed the Khazars from the area of modern Kuban and organized a state called Kazakia or Cossackia.
Some historians suggest that the Cossack people were of mixed ethnic origins, descending from Turks, Tatars, Russians, Ukrainians and others who settled or passed through the vast Steppe that stretches from Asia to southern Europe.
However some Turkologists argue that Cossacks are descendants of native Kipchak (Russian половцы) people of Ukraine, who inhabited the area long before the Mongol invasion and were closely related to modern Kazakhs. These people were highly admired for their esquestrian skills by the early Russian military. Many were hired as cavalry by Russian and Ukrainian warlords, in much the same way that they hired Black Klobuks as personal guards.