In my view, the main themes of The Cossacks are centered around the facts of cultural and ethnic integrity and the rights of all peoples to be independent and preserve their way of life.

The story takes place in the Caucasus region in the mid-nineteenth-century, as the Russian Empire, in its efforts to expand, is fighting against the indigenous peoples of the area, the Chechens. Though the Cossacks are allies of the Russians, they are, as the Chechens are, a distinct national group who wish to preserve their ethnic solidarity and sovereignty. The main character of the story, Olenin, is an upper-class Russian army officer who comes to know and admire the Cossacks and even falls in love with a Cossack young lady, Maryanka, and proposes to her. But in the end, it becomes evident that there is too great a cultural gap between them, and although Maryanka had been interested, she rejects Olenin.

Tolstoy's theme is one of contrasting the natural, uncorrupted quality of the Cossacks, both men and women, with the rather jaded milieu of upper-class Russian society. The criticism of his own social stratum is a recurrent theme in Tolstoy's oeuvre. In both War and Peace and Anna Karenina, he focuses on the hypocritical, largely irreligious behavior of the ruling Russian class. In The Cossacks, Olenin is a man who wants a new lease on life in the wild, open regions of the borderlands, and he comes to admire the independent spirit of the Cossacks and their "manly" virtues so prized by nineteenth-century male writers.

But the message is one of the insolvability of the culture clash between Great Russians and even a marginally similar group such as the Cossacks. (Great Russian is the term for the large, central Russian nationality as opposed to other groups within the Empire who may be similar and may even speak Russian, but consider themselves distinct ethnicities, as the Cossacks do.) Tolstoy regards any effort by one nation to impose its ways and value systems on another to be wrong. It would have been better for the Russians, in his view, not to have attempted the absorption of the Caucasus into the Empire. This theme is expressed much more forcefully in his later novella, Hadji Murat, but is well-defined and obvious in The Cossacks as well.