During the Interim Peace in 1940, Hallamaa traded cracked Soviet ciphers with other states to fund Finnish signals intelligence operations—for example to the Swedes in exchange for RCA transmitters. Hallamaa was promoted to lieutenant colonel and appointed the commander of Defence Command's Radio Battalion () in October 1941 during the early months of the Continuation War. Finnish radio intelligence had grown from 75 persons during the Winter War to approximately 1,000 soldiers. Reportedly, they were able to decrypt 80 percent of Soviet messages on the Finnish front. Collaboration and exchange of Soviet ciphers with Japan bore fruit when the Soviets switched their western front ciphers in late 1941 with the eastern ciphers used in Vladivostok—immediately decryptable due to the exchange. In 1942, Finnish intelligence cracked telegrams of the Allied convoys PQ 17 and PQ 18 heading to Arkhangelsk, Soviet Union and supplied the information to Abwehr, German military intelligence.