Establishment ') written on a wall in the Sremska Street in
Belgrade. Filipović was elected
mayor of Belgrade, but, refusing to pledge the oath to the King, he was not permitted to assume the office. The
Kingdom of Serbs, Croats and Slovenes (later renamed Yugoslavia) was established in late 1918 at the end of the
World War I.
Socialist movement in the territory of the new state reflected political divisions existing before the war. For example, in what was then
Austria-Hungary, the
Social Democratic Party of Croatia and Slavonia (SDPCS) came into existence in 1894, two years before the
Yugoslav Social-Democratic Party (, JSDS) was set up in
Slovene lands. The
Serbian Social Democratic Party (SSDP) was founded in 1903. In
Bosnia and Herzegovina, the
Social Democratic Party of Bosnia and Herzegovina (SDPBH) was established in 1909. The SSDP deemed it natural to serve, as the largest social-democratic party in the new state, to unify like-minded political groups in the country. The SDPBH formally proposed a merger of such parties, but the SDPCS, the JSDS, and Serbian–
Bunjevac social-democrats from
Vojvodina declined. In turn, only the SSDP and the SDPBH formally agreed to a merger by January 1919. A minority group on the left wing of the SDPCS split from the party as the Action Committee of the Left () and opted for the unified social-democratic party with the SSDP and the SDPBH. Soon afterwards, the Vojvodina social-democrats reversed their decision. The Unification congress of the
Socialist Labor Party of Yugoslavia (
Communists) (, SRPJ(k)) was held in
Belgrade on 20–23 April 1919 as consolidation on the left of the political spectrum. The new party was joined by the SSDP en masse, and by independent leftists who splintered away from various nationalist youth organisations and social democratic parties. The Labour Socialist Party of Slovenia () split from the JSDS and joined the SRPJ(k) on 13 April 1920. Clashes continued within the party between leftists and centrists – the latter favouring pursuit of reforms through a parliamentary system. The leftist faction prevailed at the second congress held in
Vukovar on 20–24 June 1920 and adopted a new statute. That aligned the party entirely with the
Communist International (Comintern), implementing all instructions received from the Comintern. Furthermore, the party was renamed the Communist Party of Yugoslavia (, KPJ) to allow its membership in the Comintern.
Filip Filipović and
Sima Marković, both former SSDP activists, were elected to lead the KPJ. By May 1920, the KPJ had about 50,000 members, and numerous sympathisers largely drawn from among 300,000 members of trade unions and youth organisations.
1920 elections and ban In the
1920 Constitutional Assembly election, the KPJ won 58 out of 419 seats. The best results were achieved in large cities, in
Montenegro and
Macedonia as a result of protest votes against the regime on account of past or expected actions coming from unemployed urban voters and from voters in regions having no other attractive national or regional opposition parties found in the Slovene lands,
Croatia-Slavonia, and Bosnia and Herzegovina. In light of difficult economic and social circumstances, the regime viewed the KPJ as the main threat to the system of government. In response to the KPJ's electoral success at the local and regional level including Belgrade and
Zagreb earlier that year in March–August, and at the national level the
Democratic Party and the
People's Radical Party advocated prohibition of communist activity. The regime saw the KPJ as the greatest impediment to realisation of views held by
King Peter I on resolution of Serbian
national question. In December 1920, KPJ-led miner strikes in Slovenia and Bosnia and Herzegovina led to suppression by the
royal army and restrictions on
communist propaganda. The violence served as a pretext for prosecution of the KPJ. On 30 December, the government issued
Obznana, a decree outlawing the KPJ. A faction of the KPJ named
Red Justice () attempted to assassinate the
Regent Alexander on 28 June, and then killed former Interior Minister
Milorad Drašković on 21 July. This led to proclamation of the Law on the Protection of the Realm turning the KPJ ban into legislation on 2 August, annulment of the KPJ seats in the national assembly two days later, and numerous covert police agents infiltrating the KPJ.
Move abroad and underground Despite the electoral success, the ban and KPJ's consequent move to covert operation took a heavy toll on the party in the next decade and a half when, faced with factional struggle, it would increasingly look to the Comintern for guidance. By 1924, the KPJ membership was reduced to 688. Additionally, some members emigrated abroad – most to
Moscow, but also to
Vienna,
Prague, and
Paris. Indeed, the KPJ held a land conference in Vienna in 1922, where the party leadership moved the year before. In the early 1920s, KPJ saw more factional struggle between its right wing led by Marković and Belgrade-based trade union leaders Lazar Stefanović and Života Milojković advocating work through legal means to regain government approval, and leftists, including Đuro Cvijić,
Vladimir Ćopić, Triša Kaclerović, Rajko Jovanović, and
Kosta Novaković, favouring
Leninist undercover struggle. The leftists also supported a federalisation of the state, while the others pushed for limited regional autonomy only. The leftists prevailed at the January 1924 Third Land Conference held covertly in Belgrade where the KPJ proclaimed the right of each nation to secede and form its national state. In June, the Comintern instructed the KPJ that self-determination should take shape of independent Slovenian, Croatian, and Macedonian republics. The stance taken by the Cominform was influenced by Moscow visit by
Stjepan Radić, the leader of the
Croatian Peasant Party (, HSS) when Radić added the HSS to the
Peasant International (Krestintern) – itself an agency of the Cominform. Furthermore, the Comintern criticised the factional clashes in the KPJ over the national question in its 1924 Resolution of National Question which linked social emancipation to national one in strategic considerations. In response, Milojković was expelled, but Marković remained a part of KPJ leadership. This changed in 1925 when he was denounced by the leader of the
Soviet Union Joseph Stalin personally before Yugoslav commission of the Comintern insisting that the KPJ must harness national movements for revolutionary aims. Regardless, the factional struggle continued. In 1927, the seat of the KPJ central committee in Yugoslavia was moved from Belgrade to Zagreb.
Leftists prevail In February 1928,
Josip Broz Tito and
Andrija Hebrang, seeking to stir the existing situation into resolution of the conflict, persuaded the delegates to conference of the Zagreb KPJ organisation to adopt a resolution seeking the Comintern to intervene and end the factional struggle in the KPJ entirely. The KPJ also led some of street protests in Croatia over assassination of Radić later that year. The
Comintern Sixth World Congress held that year sought to increase revolutionary struggle and the strategy was accepted by the KPJ at its
Fourth Congress held in
Dresden in October 1928. The appeal made at the initiative of Tito and Hebrang was accepted: Marković was expelled and his allies demoted, while new leadership was installed. Tito and Hebrang were bypassed because they were just imprisoned in Yugoslavia, and
Đuro Salaj, Žika Pecarski, and
Đuro Đaković were appointed instead as entirely Comintern-trained leadership. , Janko Mišić and Mijo Oreški, who were killed in a standoff with police on 27 July 1929 in
Samobor. In 1929, the new KPJ leadership put the Comintern's call to violence into practice, but instead of all-out revolt, the efforts were consisted of leaflets and several shoot-outs with the police. KPJ losses were heavy and included death of several significant leaders including Đaković and imprisonment of its most active members by specially convened antisubversive tribunals. In turn, the
Sremska Mitrovica Prison became a makeshift KPJ training school as the prison allowed grouping of political prisoners. On instructions from the Comintern, non-
Serb members of the KPJ were to advocate breakup of Yugoslavia as a construct of the Western Powers. However at the time, most of their efforts were invested in struggle against the JSDS and debating revolutionary merits of literature written by
Miroslav Krleža. By 1932, membership dwindled to less than 500, the KPJ maintained its leadership divided in at least two locations at all times in 1928–1935, including at least one abroad in Moscow, Prague, Vienna, or Paris. Also acting on Comintern July 1932 instructions to promote and aid national revolt in Croatia, Slovenia, Montenegro, and Macedonia, the KPJ sought to establish ties with the
Bulgaria-based
Internal Macedonian Revolutionary Organization, but the organisation was suffering from its internal weaknesses and suppressed by 1934. There were also overtures towards
Italian-based
Ustaše as a Croatian secessionist organisation. KPJ leaders praised the Ustaše-initiated
Lika uprising in 1932, hoping to steer Ustaše to the political left. Even though support for Ustaše efforts in Lika and
Dalmatia was declared through
Proleter newspapers in December 1932, the bulk of contact with them was limited to contact with fellow prison inmates trying to engage them over the shared goal of breakup of Yugoslavia.
Gorkić and turn to popular front The "ultra-leftist" line pursued since 1928 was abandoned in 1933 when
Adolf Hitler came to power in
Germany. Instead, the KPJ turned the idea of forming a
popular front together with other
anti-fascist organisations. The strategy aimed to attract broad coalition of allies since it was no longer thought feasible to achieve quick introduction of communist rule. The popular front strategy coincided with assignment of
Milan Gorkić to the KPJ leadership from his posting at the Comintern in 1932. Gorkić set about to introduce discipline to the KPJ top ranks and establish ties with the JSDS, the HSS, the
Montenegrin Federalist Party, the Slovene Christian Socialists, and pro-Russian right wing organisations in
Serbia with Moscow now advocating Yugoslav unity. This placed the KPJ at odds with the Comintern which continued to advocate breakup of Yugoslavia until signing of the
Molotov–Ribbentrop Pact in August 1939. Still, Gorkić largely stayed out of Yugoslavia. In 1934, he appointed Tito, just released from jail, to organise secret KPJ congress in
Ljubljana later that year. Gorkić was appointed the general secretary of the KPJ in 1936, with
Sreten Žujović and
Rodoljub Čolaković as
central committee members. Tito was appointed by the Comintern as the organisational secretary of the KPJ in Moscow in September of the same year and he moved to Vienna a month later. In July 1937, Gorkić was summoned from his Paris base to Moscow where he was arrested. In addition to him, there were about 900 communists of Yugoslav origin or their supporters in the Soviet Union who fell victim to the Stalin's
Great Purge as did 50 other KPJ officials posted in Moscow including Cvijić, Ćopić, Filipović, Marković, and Novaković. The Soviet subsidy to the KPJ was suspended. The move left Tito in de facto control of the KPJ as his position was ranked second only to the one held by Gorkić.
Tito assumes power Tito spent 1937 and early 1938 in Yugoslavia organising the KPJ there as a disciplined covert organisation drawing new members loyal to the communist ideas and Tito personally from all nations within Yugoslavia, except
Macedonians. During this period, Tito intervened in conflict among groups of KPJ members incarcerated in Sremska Mitrovica. The conflict centred on the popular front strategy advocated by Hebrang and supported by
Moša Pijade,
Josip Kraš, and
Đuro Pucar and denounced by Petko Miletić backed by
Milovan Đilas and
Aleksandar Ranković – the latter labelled
Wahhabites by Pijade because of their radicalism. The conflict escalated to an attempt to kill Hebrang. Tito worked with Pijade to arrange a compromise by including Đilas and Ranković in the temporary KPJ leadership along with Croatian moderate popular front supporters Kraš and Andrija Žaja as well as Soviet-educated
Slovene Edvard Kardelj. In 1937, the Comintern compelled the KPJ to formally establish the
Communist Party of Croatia (, KPH) and the
Communist Party of Slovenia (). The two parties were nominally independent, but actually within the KPJ. This was later the precedent for establishment of communist parties in other parts of Yugoslavia. Still the KPH leadership headed by Kraš and Žaja came into conflict with Tito in 1938 when the KPH supported the HSS instead of the Party of the Working People as the KPJ front founded for participation in
1938 parliamentary elections. The temporary leadership put together by Tito remained largely unchanged when Tito received the Comintern mandate to lead the KPJ in 1939. Miletić was released from prison that year and sought to replace Tito. Months later he disappeared after he was summoned to Moscow and arrested by the
NKVD as a victim of a series of purges in the KPJ in 1937–1940 which strengthened Tito's position. In 1940, the KPJ successfully completed the campaign to diminish influence of Krleža and his literary adherents who were advocating
Marxist ideas and opposed
Stalinisation fearing
totalitarianism. Also, Tito removed Kraš and Žaja from the leading positions in the KPH and replaced them by
Rade Končar. In October 1940, the Fifth Land Conference of the KPJ was held covertly in Zagreb, as the final act of Tito's campaign to assume full control of the party. The conference represented a full takeover of now organisationally stronger, centralized, disciplined, and
bolshevized, but politically isolated KPJ by Tito in full alignment with the leftist line pursued by the Comintern at the time. The national question was placed at the centre of the KPJ policy at the conference where Tito criticised long gone Marković and Gorkić for lack of understanding of the issue. As Tito consolidated his control, the KPJ membership grew to 6,000 in 1939 and to 8,000 by 1941, with many more other supporters. The final months of 1940 were marked by militarisation of politics in Yugoslavia leading to incidents such as the armed clash between the KPJ and the far-right
Yugoslav National Movement in October leaving five dead and 120 wounded. The structural changes of the KPJ, strategic use of the national question and social emancipation to mobilise supporters made the party ideologically and operationally ready for armed resistance in the approaching war. ==Armed resistance==