The Ural Cossack Host was a cossack host formed from the Ural Cossacks -- those cossacks settled by the Ural River. Their alternative name, Yaik Cossacks, comes from the old name of the river.
The Yaik (Ural) Cossacks although speaking Russian and identifying themselves as being of primarily Russian ancestry also incorporated many Tatars into their ranks. According to Peter Rychckov some these Tatars called themselves Bulgarians of Khazar origin, and the first Yaik Cossacks, including these Tatars and Russians, existed by the end of 14th century. These Tatars might be both Chuvash people and Mishari (Meschera in Russian, Miser in Tatar language), the latter had not only Moslems and Jews, but Christians among them to facilitate their merge with Russians Meschera were important on Don as well. Later, as Pushkin wrote, a lot of Nogai joined Yaik Cossacks. Twenty years after the conquest of the Volga from Kazan to Astrakhan, in 1577 Moscow sent troops to disperse pirates and raiders along the Volga (one of their number was Ermak). Some of these fled southeast to the Ural River and joined Yaik Cossacks. In 1580 they captured Saraichik together. By 1591 they were fighting for Moscow and sometime in the next century they were officially recognized. In 1717 they lost 1,500 men on the Alexander Bekovich-Cherkassky expedition to Khiva. A census in 1723 showed 3,196 men fit for military service.
A Cossack host (Ukrainian: Козаче військо, kozache viysko), sometimes translated as Cossack army, was an administrative subdivision of Cossacks in Ukraine. The word host is an archaic word for army.
The Cossack host consisted of a certain territory with Cossack settlements that had to provide military regiments for service in the Imperial Russian Army and for border patrol. Usually the hosts were named after the regions of their dislocation. The stanitsa, or village, formed the primary unit of this organization.