According to historian Anne Applebaum, approximately 6,000 katorga convicts were serving sentences in 1906 and 28,600 in 1916 [REF].
After having appeared as an instrument and place for isolating counterrevolutionary and criminal elements, the Gulag, because of its principle of "correction by forced labor", quickly became, in fact, an independent branch of the national economy secured on the cheap labor force presented by prisoners [REF].