In 1921, Lukanov graduated in law from the Clement of Ohrid University of Sofia to become a lawyer in Pleven. During the White Terror which ensued in the wake of the St Nedelya Church assault of 1925, he was sentenced to four years in prison, but amnestied in 1926. Shortly thereafter, Lukanov moved to the Soviet Union, where he worked as a clerk at a construction company. From 1927 to 1944, he was on the books of the All-Union Communist Party (Bolsheviks), later known as the Communist Party of the Soviet Union. In 1936, Lukanov left for Spain, where he remained until 1939. In Spain, Lukanov took various governing positions within the International Brigades that assisted the Republican forces in the Spanish Civil War. After his return to Moscow, Lukanov worked at the Comintern and from 1941 on at the Hristo Botev Bulgarian-language radio.