the creator died before January 1, 1943 and was fighting in the Great Patriotic War (June 22, 1941 - May 9, 1945) or working during the war (primarily concerns authors who were born before 1930), or
it was published anonymously before January 1, 1947 and the creator has not asserted his authorship in the following 70 years, or
the creator died before January 1, 1947, and was not fighting or working during the war
(Article 1281 of the Russian Civil Code; Article 6 of Federal Law 231-FZ from December 18, 2006).
In addition, a Russian or Soviet work that is in the public domain in Russia is in the public domain in the U.S. only if it was in the public domain in Russia in 1996, and no copyright was registered in the U.S. (This is the combined effect of Russia's joining the Berne Convention in 1995, and of 17 USC 104A with its critical date of January 1, 1996.)