Female sexual slavery was extremely common in the Ottoman empire and any child of a female slave was just as legitimate as any child born of a free woman. This means that any child of a female slave could not be sold or given away. However, due to extreme poverty, some Circassian slaves and free people in the lower classes of Ottoman society felt forced to sell their children into slavery; this provided a potential benefit for the children as well, as slavery also held the opportunity for social mobility. If a harem slave became pregnant, it also became illegal for her to be further sold in slavery, and she would gain her freedom upon her current owner's death. Slavery in and of itself was long tied with the economic and expansionist activities of the Ottoman empire. There was a major decrease in slave acquisition by the late eighteenth century as a result of the lessening of expansionist activities. War efforts were a great source of slave procurement, so the Ottoman empire had to find other methods of obtaining slaves because they were a major source of income within the empire. The Caucasian War caused a major influx of Circassian slaves into the Ottoman market and a person of modest wealth could purchase a slave with a few pieces of gold. At a time, Circassian slaves became the most abundant in the imperial harem.