The world has grown quite used to the fact that almost all Soviet export and import transactions are conducted by specialized state foreign trade organizations (ob'edineniia, "combines" or "associations") subordinate to a single state agency, the Soviet Ministry of Foreign Trade. The idea of such a "state monopoly" of foreign trade was originally put forth by Lenin and instituted by a decree of April 1918. It was intended primarily as a means of national economic defense: to protect the fledgling Soviet economy against anticipated imperialist exploitation. This was before the introduction of a centrally planned economy, and before even the introduction of War Communism (1918-21) with its program of state ownership of the "commanding heights" of the economy.
During the period of the New Economic Policy (1921-28), with its emphasis on some forms of private domestic trade, the "foreign trade monopoly" was vigorously challenged (by Stalin among others), but Lenin insisted upon retaining it. In the subsequent era of full-scale central planning when agriculture was collectivised and virtually all production and distribution of industrial goods was placed in the hands of specialized ministries ("people's commissariats"), each responsible for a particular branch of the economy, it seemed quite natural to leave exporting and importing to one such ministry and a number of subordinate combines, each with its own monopoly of export and/or import of particular types of products.
Harold J. Berman,
8 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vjtl/vol8/iss4/7