lot of their cultural traits. In the 16th century, a great organizer, Dmytro Vyshnevetsky, a Ukrainian noble, united these different groups into a strong military organization. The Zaporozhian Cossacks had various social and ethnic origins but were predominantly made up of escaped serfs who preferred the dangerous freedom of the wild steppes, rather than life under the rule of Polish aristocrats. However, townspeople, lesser noblemen and even Crimean Tatars also became part of the Cossack host. They had to accept Eastern Orthodoxy as their religion and adopt its rituals and prayers. The nomadic hypothesis was that the Cossacks came from one or more nomadic peoples who at different times lived in the territory of the Northern Black Sea. According to this hypothesis the Cossacks' ancestors were the Scythians, Sarmatians, Khazars, Polovtsy (Cumans), Circassians (Adygs), Tatars, and others. The nomadic hypothesis of the origin of the Cossacks was formed under the influence of the Polish historical school of the 16th-17th centuries and was connected with the theory of the Sarmatian origin of the gentry. According to the tradition of deriving the origin of the state or people from a certain people of antiquity, the Cossack chroniclers of the 18th century advocated the Khazar origin of the Cossacks. With the expansion of the source base and the formation of historical science, nomadic hypotheses were rejected by official historiography. For the first time, Alexander Rigelman pointed out the imperfection of the hypothesis. In the 20th century, the Russian scientist Gumilyov was an apologist for the Polovtsian origin of the Cossacks. Within the Polish–Lithuanian Commonwealth In the 16th century, with the dominance of the Polish–Lithuanian Commonwealth extending south, the Zaporozhian Cossacks were mostly, if tentatively, regarded by the Polish–Lithuanian Commonwealth as their subjects. Registered Cossacks were a part of the Commonwealth army until 1699. Around the end of the 16th century, relations between the Polish–Lithuanian Commonwealth and the Ottoman Empire, which were not cordial to begin with, were further strained by increasing Cossack aggression. From the second part of the 16th century, the Cossacks started raiding Ottoman territories. The Polish government could not control the fiercely independent Cossacks but, since they were nominally subjects of the Commonwealth, it was held responsible for raids by their victims. Reciprocally, the Tatars living under the Ottoman rule launched raids in the Commonwealth, mostly in the sparsely inhabited south-east territories of the Ukraine. Cossacks, however, were raiding wealthy