sentences:  In 1839 he led an invasion of the Khanate of Khiva, in part to free Russian slaves captured from the Russian frontiers on the Caspian Sea and sold by Turkmen raiders, but also as an attempt to extend the Russian borders in the direction of Central Asia while the British Empire was entangled in the First Anglo-Afghan War of 1839-1842.Perovsky's expeditionary force consisted of 5,200 infantry and 10,000 camels.Due to poor planning and a bit of bad luck, they set off southwards, in November 1839, into one of the worst winters in memory, and had to turn back in February 1840.