1918 protest in Zagreb

In the final days of the World War I, on 5–6 October 1918, political parties representing Croats, Slovenes, and Serbs living in Austria-Hungary organised the Zagreb-based National Council of Slovenes, Croats and Serbs to achieve independence from the empire. The National Council proclaimed the State of Slovenes, Croats and Serbs encompassing the Slovene Lands, Croatia-Slavonia, Dalmatia, and Bosnia and Herzegovina,[1] and authorised the Yugoslav Committee, an interest group advocating unification of previously Habsburg South Slavic areas with the Kingdom of Serbia, to represent the council abroad.[2] National Council president Anton Korošec left Zagreb for a conference in Geneva with Serbian representatives to discuss the method of unification.[3]

At the time, Austro–Hungarian deserters termed Green Cadres were causing a crime wave in the countryside.[4] By September 1918, there were about 50,000 Green Cadres among the Croats, Serbs, and Bosniaks. Most of them were active in Croatia-Slavonia,[5] where violence peaked between 24 October and 4 November.[6] The period also saw a mutiny in Požega. In nearby Orahovica, two Austro-Hungarian regiments, one Bohemian and one Dalmatian fought against each other.[7] Officials in the town reported that some of the soldiers sided with the Bolsheviks.[8] The violence quickly spread and elements of the 23rd Regiment and the 28th Regiment of the Royal Croatian Home Guard joined in looting Osijek.[7] Mutineers also led looting in Petrovaradin, Pakrac, Daruvar, and Županja, although peasants and the (mostly peasant) Green Cadres were responsible for most of the pillaging and looting.[7]

The National Council hesitated to condemn the violence,[6] and its attempts to stop the looters by deploying ad-hoc, locally raised militia were ineffective since many militiamen were also looting.[9] Therefore, the National Council relied on Serbian prisoners of war (captured by the Austro-Hungarian Army during the war), and sent a delegation to the Royal Serbian Army command on 5 November to request its troops to restore order in Croatia-Slavonia.[10] The National Council, by then dominated by the Croat-Serb Coalition led by Svetozar Pribičević,[11] blamed the unrest partly on Bolsheviks and the Croatian People's Peasant Party (HPSS) led by Stjepan Radić. The association of the HPSS with the popular discontent later helped propel the HPSS to the position of the most successful political party among the Croats in the interwar period.[12] The peasants actively involved in the October–November unrest, misidentifying republicanism as the abolition of military service and taxes, cited it as their ultimate political objective.[13]

Map of lands forming the Kingdom of Serbs, Croats and Slovenes

There were two main approaches to the unification of the South Slavs. While Ante Trumbić's Yugoslav Committee advocated a federal system of government, the Prime Minister of Serbia Nikola Pašić wanted a centralised state.[14] Pašić threatened to conquer and annex the Serb-inhabited territories of Austria-Hungary to create a Greater Serbia unless Trumbić accepted a centralised state.[15] Under pressure from the Triple Entente, Pašić agreed to support a federal South Slavic state during the November 1918 conference in Geneva,[16] but Serbia repudiated the agreement either because of Prince Regent Alexander's opposition,[17] or in a scheme devised by Pašić to deflect Entente pressure and undermine Korošec's authority.[18]

Shortly after the conclusion of the Geneva conference, the National Council announced it had thwarted an attempted coup d'état for which it arrested General of the Infantry Anton Lipošćak.[19] The Italian Army seized Rijeka and approached Ljubljana.[20] Without means to stop the Italian advance, the National Council feared that the Italian presence on the eastern shores of the Adriatic would become permanent.[21] The National Council dispatched a delegation to Prince Regent Alexander to quickly arrange unification of Yugoslavia on a federal basis. The delegation ignored the National Council's instructions to demand constitutional safeguards when it addressed the Prince Regent on 1 December. The Prince Regent accepted the unification offer on behalf of Peter I of Serbia,[22] and the Kingdom of Serbs, Croats and Slovenes was established without any agreement on the nature of the union.[23]

Photograph of a Royal Serbian Army unit arriving to the Ban Jelačić Square in Zagreb in late 1918.

The National Council established the National Guard on 27 October 1918 in preparation for the Croatian Sabor meeting that declared secession from Austria-Hungary two days later. The National Guard consisted of volunteers from university guard organisations and Croatian and Serb Sokol associations, subordinated to the Commission for Public Order and Security in Zagreb headed by Budislav Grga Angjelinović and directly commanded by Lav Mazzura. The force was augmented by a detachment of former Austro-Hungarian Navy sailors.[24] Attempts to organise the National Guards in the countryside to combat civil disorder proved ineffective.[9]

The State of Slovenes, Croats and Serbs formally established its military on 1 November, three days after the declaration of independence, from Austro-Hungarian units based in the territory of the new state. On 6 November, the 25th Regiment of the Royal Croatian Home Guard and the 53rd Regiment of the Common Army based in Zagreb swore an oath of allegiance to the National Council. The council deemed the soldiers returning from the war after that date also bound by the same oath.[25] The 25th Regiment had just returned from fighting in to capture Međimurje on behalf of the National Council, and both regiments maintained security in Zagreb without incident. Nonetheless, many soldiers based in Zagreb supported a republic; republican ideas spread under the influence of Radić and returnees from Russia in the aftermath of the October Revolution.[26] In early December 1918, the 25th Regiment commanded by Colonel Milivoj Kućak[27] had 210 officers and 578 soldiers stationed in Zagreb barracks of the Royal Home Guard in the Ilica Street, while the 53rd Regiment had 442 troops stationed in the city, in the Rudolf barracks.[28] The 53rd Regiment, commanded by Colonel Mirko Petrović,[29] the 37th Field Artillery Regiment of the former Common Army, and the 6th Field Artillery Regiment of the Home Guard were also stationed in the city.[30] The 37th Field Artillery Regiment had 22 officers and 142 soldiers, while the 6th Field Artillery Regiment had 46 officers and 21 soldiers in Zagreb.[31] The National Council-established National Guard had about 500 armed members in Zagreb at the time,[32] augmented by a 1254-strong regiment composed of former Serbian Army prisoners-of-war.[33] In November, Lieutenant Colonel Dušan Simović was assigned to Zagreb as the envoy of the Serbian Army,[34] and the 3rd Battalion of the 7th Regiment of the Serbian Army arrived in Zagreb by the end of the month.[35]

In the afternoon of 5 December, some soldiers of the 53rd Regiment left the Rudolf barracks in western Zagreb and set out towards Ban Jelačić Square.[28] En route, they stopped before the Home Guard Barracks in Ilica Street where some soldiers of the 25th Regiment joined the march.[40] Civilians also joined the soldiers.[25] The soldiers brought rifles and two machine guns from each barracks[41] and were accompanied by the twelve-strong military band of the 25th Regiment.[28] The marchers intended to declare a free Croatian republic, spurred on by perceived provocative behaviour at celebrations of unification.[37] The subsequent indictment for the act of mutiny specified 250 soldiers participating, but the actual number is likely to be about 400, 200 from each regiment.[42]

Protesting the unification with Serbia,[36] the soldiers walked down Ilica Street carrying a flag of Croatia and shouting "Long live the republic!", "Long live Radić!", "Down with King Peter!", "Down with the dynasty!", "Long live the peasant party!", "Down with militarism!",[43][37] "Long live Croatian republic!", and "Long live Bolshevik republic!". Authorities later also reported that the demonstrators called out for release of General Lipošćak.[44] According to Croatian historian Mislav Gabelica, it is unclear if the soldiers were protesting against the unification itself or the method by which it was carried out. Gabelica also argues that the protest was in part spurred on by various causes for discontent such as widespread poverty and anarchy in the country as well as by external actors such as by Italian intelligence services.[45]

Most sources agree that the protesting soldiers reached Ban Jelačić Square at 2 p.m.[46] Some troops loyal to the government were deployed at the end of Ilica to prevent people from entering the square, but they quickly gave way.[27] Upon reaching the square, the soldiers of the 25th and the 53rd regiments set up two machine guns at the centre of the square, and two at the start of Ilica – near the Gajeva Street and Oktogon respectively.[47] The military band took position at the square near the Duga Street (Radićeva Street today) and played Lijepa naša domovino.[48]

Sketch of approximate positions of machine guns at the Ban Jelačić Square in Zagreb on 5 December 1918: 1 - House Popović, 2 - House No. 6 (Rosia-Fonsier), 3 - House Feller, 4 - Oktogon, 5 - Jelačić monument; Erroneous reports: 6 - House No. 27, 7 - Foundation Hospital, 8 - House Gnezda

The authorities were informed about the planned protest at the latest at 11:30 a.m. on the day of the protest,[49] and cleared the square of people before the soldiers arrived.[50] Armed National Guardsmen and Sokol volunteers were waiting for the soldiers and civilians who joined the protest, taking cover in the surrounding buildings.[46] According to contemporary government reports, 60 National Guardsmen were deployed on the north side of the square, in House Popović (then at number 4, the numbers have changed since) and at house number 6 – with a machine gun set up in each building. According to that report, 20 troops were at the House Popović, while the rest, together with Angjelinović, took up positions at the other building.[51] According to the 1926 testimony of Sergeant Dragutin Mačuka, the government deployed 160 troops (National Guards and Sokol volunteers) to the square. The headquarters were set up in the house at number 6 with additional troops at the House Popović and the House Feller (at number 21, at the corner of the Jurišićeva Street) on the east side of the square.[52] Mačuka's estimate of the government strength is supported by testimony of a Sokol volunteer, Branko Kojić, who said 60 Sokol volunteers and 100 National Guardsmen were deployed.[53] First there were brief negotiations.[46] According to witness statements, Kućak and Lieutenant Colonel Slavko Kvaternik went to House Popović and attempted to calm the situation down. According to Kvaternik, they persuaded Mazzura to tell the National Guardsmen in that house not to fire. Kvaternik's statement is contradicted by others who identified civilian Zdravko Lenac as commander of the National Guardsmen at the House Popović.[54]

According to trial testimony, the soldiers of the 25th and the 53rd regiments captured House Popović and the machine gun placed there. Various testimonies disagreed as to whether the second machine gun was placed at a balcony of the adjacent house (number 5) or at the house number 6[lower-alpha 1] as indicated in official contemporary reports. The witnesses agree that the soldiers left the House Popović to capture another machine gun, that a gunfight erupted inside that building, and the machine gun fired on soldiers in the square.[56] A later inspection of bullet pockmarks left on facades revealed that the house number 6 was the main target of the soldiers' fire, and other testimonies placed Angjelinović in that house, commanding the machine gun crew to fire on the soldiers.[57] Kvaternik and other witnesses indicated that a third machine gun fired from the House Feller and killed a soldier manning a machine gun set up by the mutineers at the foot of the Josip Jelačić monument on the square.[58][59] In his 1947 testimony, Kvaternik said the National Guards had a machine gun on the south side of the square at the house number 27 at the corner of present-day Praška Street, but no other source supports that claim.[58]

The skirmish ended at about 3 p.m.[46] Most of the protesters scattered and fled, but some survivors were captured.[28] Eighteen people died in the gunfight or of their wounds. The deaths included two National Guardsmen (both Sokol members), an unidentified Serbian soldier whom Simović says was not an active participant in the clash,[60] and two civilians.[61] On 7 December, Simović requested his superiors to deploy the rest of the 7th Infantry Regiment to Zagreb for security reasons.[62] Military prosecutor's and forensic experts' reports of 6 December indicated 15 killed and 13 wounded. Three of the injured died of their wounds after the report was published.[63] A subsequent trial identified Lance Corporal Rudolf Sentmartoni as the ringleader of the soldiers' protest, together with Sergeant Ivan Perčić, Corporal Martin Murk, an unnamed lance corporal in the 6th Field Artillery Regiment and an unidentified civilian. None of them were apprehended except Perčić, who was convicted for mutiny and sentenced to six years in prison.[64] In 1941, Horvat wrote about the clash. Unlike other sources, Horvat stated that there were two machine guns – one firing from the roof of House Gnezda nextdoor to the House Feller and one from the top floor of a hospital (since replaced by 1 Ilica Street building). Reports on the direction of machine gun fire given by surviving soldiers contradict Horvat.[65]