Rules of conduct for Soviet submarines when approaching British warships since 1921

The Commissioner of the United States at Riga, Latvia sent on 25 January 1922 to the Secretary of State at Washington a a secret order dated 31 March 1921 how Bolshevik submarines were to act when being in the vicinity of British warships. The order was a result of the British-Soviet Russian Trade Agreement effected on 16 March 1921. It was only allowed to approach a British warship at daylight, surfaced and showing the R.S.F.S.R. flag at the stern.

Source

Records of the Department of State Relating to Internal Affairs of Russia and the Soviet Union, 1910-29. Naval Affairs, Navy, Navy Vessels: 861.30 .(861.31 Naval Maneuvers; 851.32 Personnel); 861.33 Movements of Navy Vessels; 861.34 Equipment and Supplies): 861.39 - 861.345. Micro film 316 roll 92.