The Independent State of Croatia (NDH) was founded on 10 April 1941 during the invasion of Yugoslavia by the Axis powers. The NDH consisted of most of modern-day Croatia and Bosnia and Herzegovina, together with some parts of modern-day Serbia. It was essentially an Italo-German quasi-protectorate, as it owed its existence to the Axis powers, who maintained occupation forces within the puppet state throughout its existence.^[1]

According to the Treaties of Rome between Benito Mussolini and Ante Pavelić, Italy annexed Zone I, and Zone II was demilitarized.^[2] After that, Italy pulled out the bulk of its army from Zones II and III.^[3]

In the weeks following the invasion, the Communist Party of Yugoslavia (Serbo-Croatian Latin: Komunistička partija Jugoslavije, KPJ) managed to tie up its cells. Some members of the KPJ and the Union of Communist Youth of Yugoslavia (Serbo-Croatian Latin: Savez komunističke omladine Jugoslavije, SKOJ) were returnees from the defeated Royal Yugoslav Army, including Zdravko Čelar, Slavko Rodić, and Rajko Bosnić. There were also students like Ilija Došen, and workers and refugees from Hungarian-occupied Bačka, including Milutin and Pero Morača.^[4] KPJ committees in Drvar and Bosansko Grahovo succeeded in obtaining rifles, light machine guns, and ammunition belonging to the surrendered Royal Yugoslav Army, and hid them from German, Italian and later Ustashe searches.^[5] Independent of the efforts of the KPJ, local peasants also hid arms.^[6]

During late April and early May, Ustashe couldn't easily consolidate their rule in an area with a predominantly Serbian population. They were only able to achieve that with Italian support and a Ustashe squad brought in from Herzegovina.^[5] Italian units left Drvar area in the beginning of June.^[5]

After the NDH consolidated its rule in Drvar at the end of May 1941, Ustaše imprisoned many Serbian men from Drvar and began with preparation to imprison and indiscriminately kill all Serbs from Drvar.^{[7][non-primary source needed]}

Through June, communists across Bosanska Krajina continued to prepare for an uprising. Ljubo Babić was chosen to be the head of the military committee for Drvar, and Ilija Došen was chosen for Bosanski Petrovac.^[8] Axis invasion of the Soviet Union encouraged locals to accelerate preparations.^[9] Ustashe authority anticipated rebellion, so reinforcements were brought to the area. The Party advised Drvar workers who were in danger of being arrested to leave Drvar and hide in nearby villages. ^[10] On 17 July, communists set up the Headquarters of Guerilla Detachments for Bosanski Petrovac with Zdravko Čelar in command, Vaso Kelečević as his deputy and Ilija Došen as the political commissar. ^[11] The following day, the Headquarters for Drvar was established, with Babić as commander and Milutin Morača as his deputy.^[11] Between 20 and 26 July, the first detachment of fifty men was formed in the village of Kamenica (commander Jole Marić, political commissar Nikola Kotla). In the following days, new detachments were formed in the villages of Javorje (commander Mile Kecman, deputy Slavko Rodić) and Crvljivci (commander Vlado Morača).^[12] In Bosansko Grahovo, a detachment was formed, with Simo Bajić as commander. In the village of Trubar, a detachment was formed, with Nikola Rodić as commander and Pero Boltić as commissar.^[12] There were also smaller detachments.^[12]

The Ustaše genocidal policy resulted in a mass uprising of Serbs which began on 27 July 1941 in Bosnian Krajina (Western Bosnia) and Lika simultaneously.^{[citation needed]}

The uprising in Drvar was inspired by Orthodox priest Ilija Rodić, worker Ilija Desnica and teacher Uroš Drenović.^{[13][non-primary source needed]} Since 22 June 1941, more than 2 months after Axis invasion of Yugoslavia, the communists also planned to organize an uprising in Bosnian Krajina on 1 August 1941.^{[14][non-primary source needed]} Notably, the Central Committee of the Communist Party of Croatia pushed for rebellion only after the uprising was in its advanced stages in an attempt to shape the character of the uprising into one that pushed for communist ideals rather than mere survival.^{[15][attribution needed]}

Initially, the Serbian uprising had no ideological background because it was a struggle for physical survival. While Croatian reports referred to the rebellion as Chetnik-Communist action, rebels simply considered themselves rebels or guerilla.^{[16][attribution needed]} Only in September, after the Stolice conference, would communist rebels adopt the name "partisans", and nationalists around same time begun calling themselves "chetniks". Because the vast majority of rebels in Krajina and the Independent State of Croatia were Serbs in 1941 to 1942, Ustashe propaganda initially called all rebels chetniks.^{[citation needed]}

One detachment of rebels were under command of Vlado Morača.^{[17][non-primary source needed]} Some of the rebel units were under the control or influence of the communist party while many others were not, including a group of rebels under command of Nikica Kecman.^[18] The commanders of the rebel units of Drvar district included Mane Rokvić and Branko Bogunović.^[19] Some participants of the uprising became Chetniks, like Mane Rokvić, Uroš Drenović^{[20][non-primary source needed]} and Ilija Desnica.^{[21][non-primary source needed]} The rebel forces during the uprising eventually numbered 4,000 men.^[22] The Serb rebel detachments were armed with 270 rifles and 7 machine guns.^{[23][non-primary source needed]}

The Drvar garrison had a total of 400 Ustaše and Croatian Home Guard soldiers of Independent Croatia.^[24]

The Italian Military Intelligence Service reported that the uprising began on 26 July 1941 when rebels attacked isolated gendarmerie stations, railroads and communication lines.^[25] The rebels cut all telephone poles between Drvar, Grahovo and Knin.^{[26][non-primary source needed]}

On 26 July 1941, in a road ambush near village Pasjak, a group of Serb nationalists, including Nikica Kecman and three of his men, killed Croatian major Ferdinand Konrad who was travelling from Drvar to Prijedor by car.^{[27][28][non-primary source needed][18]} The ambush was actually targeted at logornik Kuharski, who had issued an order to kill 40 notable Serbs from Drvar, but was still considered a success as it ignited the uprisings in Lika and Krajina.^{[29][non-primary source needed]}

The Ustaše and Home Guard forces soon arrived from Drvar by train and harassed the local population until they were forced to retreat by guerilla groups of rebels from the hamlets of Crvljivica and Zaglavica.^{[30][non-primary source needed]} The rebels knew the Ustaše would return. Thus, their Headquarter of Guerilla Detachments for Bosnian Grahovo and Surrounding (Serbian: Штаб герилских одреда за Босанско Грахово и околину) decided to start the uprising early the following day, on 27 July 1941.^[31][32]

The plan for attack on Drvar was prepared by Slavko Rodić, a partisan.^{[33][non-primary source needed]}

One of the rebels was local schoolteacher Lazar Tešanović^{[34][non-primary source needed]} who read the order for attack on Drvar using a battery lamp.^{[35][non-primary source needed]} The beginning of rebel attack was signaled with a fire of signal gun from the citadel on Šobića Glavica at 3:30 AM.^{[23][non-primary source needed][17][non-primary source needed]} The detachment commanded by Morača attacked a Ustaše unit in Oštrelj, a village on the road toward Bosanski Petrovac which became the first populated place under rebel control during uprising.^{[17][non-primary source needed]} Rajko Bosnić, who would later be recognized as a People's Hero of Yugoslavia, distinguished himself as a member of Crvljevičko-Zaglavički detachment.^{[36][verification needed]}

The first platoon was given the order to capture Ustaše barracks in the pre-war Apprentices' Home building.^{[37][non-primary source needed]}

The mass uprising in Bosnian Krajina first started in Drvar on 27 July when three rebel detachments from Kamenica, Javor and Crvljivica, accompanied by hundreds of armed peasants, captured a garrison of 400 Ustaše and Home Guard soldiers in Drvar.^[38][24] The rebels were under the command of Mane Rokvić.^{[39][unreliable source?][40][non-primary source needed]} In Drvar, Ustaša Mijo Sarić fired heavy machine guns at rebels from the tower of local church.^{[41][non-primary source needed]}

The rebels captured all surviving enemy soldiers, including 120 members of Croatian Home Guard, as well as a substantial quantity of arms and ammunition.^[42][43] The Croatian commanders, logornik Kuharski and Ustaša Sarić, known as Šeponja, managed to escape.^[44]

The rebels, fueled by resentment against earlier massacres of Serbs, committed numerous massacres of war prisoners, as well as Muslim and Croatian civilians. The number of victims are estimated to be between 1,000 and over 3,000 people. Some massacres occurred on the first day of the uprising, such as the Trubar massacre and Bosansko Grahovo massacre, while others happened later, such as the Krnjeuša massacre and Kulen Vakuf massacre.^{[citation needed]}

On 27 July 1941, the rebels captured Oštrelj and Bosansko Grahovo under the command of rebel leader Branko Bogunović.^{[45][46][non-primary source needed]} The Drvar uprising had a large impact on the development of the Srb uprising in Lika, where the largest number of communists were present, along with many armed people from Srb and the surrounding area.^{[47][non-primary source needed]} On the first day of the uprising, Serbian rebels from Bosnian Krajina and Lika managed to seize control over territory which was 70 kilometres (43 mi) long and 45 kilometres (28 mi) wide.^{[48][non-primary source needed]}

The rebel unit commanded by Simo Šolaja captured the gendarmerie station in Pljeva, while rebels from the southern part of Mrkonjić Grad municipality and rebels from Glamoč and Pljeva captured the gendarmerie stations in Gerzovo and the villages of Čardak, Podgorje, Gerzovo, Dragnić, Trnovo, Baraći, Pecka, Medna and many other villages in the southern part of Mrkonjić Grad municipality.^[49]

The rebels immediately established the command of the Drvar municipality, which operated until 25 September 1941 and was reestablished at the beginning of July 1942 when Drvar was captured by communist forces.^[50] The headquarter of joint Partisan-Chetnik rebels was housed in Drvar.^{[51][non-primary source needed]} The Chetnik commander Uroš Drenović was subordinated to this joint headquarter.^{[51][non-primary source needed]} The partisans organized revolutionary court in Drvar.^[52]

Since the first days of the uprising in Bosnian Krajina, the communists gradually forged their Partisan republic, and on 30 July 1941, established a Military-Revolutionary Council that became the supreme governing institution for the whole region.^{[53][verification needed]} The Partisans referred to this territory as Drvar Republic.^{[54][non-primary source needed]}

In the regions of Bosansko Grahovo and Mrkonjić Grad, the influence of the communists was not as strong as in Drvar, and Chetnik representatives like Uroš Drenović neutralized communist attempts to impose their ideology on rebels and consolidate their own forms of government.^[55]

To suppress the uprising, Croatian authorities sent eight battalions and several artillery batteries to Drvar.^[25] Both Italian and German intelligence reports concluded that the Drvar uprising had "Communist and Serbian" character and that the main reason for uprising was the Ustaša terror of the Serbian population.^[25] The units engaged by Croatian authorities were unable to suppress the uprising.^[25] Italy used the uprising to try to expand the territory of NDH under Italian control deeper into Western Bosnia.^[56] As the uprising spread from Drvar to other parts of Western Bosnia, the Serb rebels in Banja Luka, Jajce, Prijedor, Livno, Dubica and Sisak were actually supported by Italy, both in politics and in arms.^[22] On 26 August 1941, NDH and Italy agreed that the Second Italian Army would occupy and pacify rebels in the second and third zone.^[57] Thus, Italy supported Serbian rebels to create an opening to establish its influence beyond the zones they occupied per formal agreements.^[57]

Similar to the uprising in Montenegro, the rebels disagreed about their further actions. Nationalist rebels concluded that it was in the best interest of the people to accept integration of the territory into the Italian zone of interest, where they would be protected from Ustaše genocide. The Chetnik leaders wished to save Serbs from their most feared and violent enemy - Ustaše, even if they had temporarily to accept the rule of Italians and Germans.^[58] The leaders of rebellion, Mane Rokvić, Vlado Morača and Ilija Desnica, organized a gathering of the people in the village of Zaglavice and, in presence of Italian soldiers, insisted that nobody should attack Italians.^[59] The Italians occupied Drvar and the region previously held by rebels on 26 September 1942. The Partisans destroyed the cellulose factory in Drvar before they retreated in front of advancing Italian units in September 1941.^{[60][non-primary source needed]}

The Communist Party insisted on proceeding with rebellion in order to carry on with the communist revolution. Rebels who disagreed were quickly labeled as traitors and representatives of Greater Serbian bourgeois elements.^{[61][non-primary source needed]} The communists targeted those who did not support their revolutionary methods and soon executed Ilija Desnica and many other non-communist rebel leaders. The priest Ilija Rodić, one of the initiators of the uprising, was later also killed by communists.^[62]

After Italians captured the territory previously held by the rebels, the Chetniks gained the confidence of the local population, especially in central Bosnia and the region of Bosansko Grahovo.^{[63][verification needed]} The local population organized a gathering on 14 November 1941 in Crni Potoci, and agreed on decisions against communist violence after communists secretly killed Ilija Desnica.^[64] To fight against the Chetniks, the communists established the Grmeč Proletarian Company at the beginning of March 1942 in Srpska Jasenica.^{[65][verification needed]} On 1 April 1942 the communists established the Kozara Shock Anti-Chetnik Battalion by recruiting 400 Partisans selected from the best fighters.^{[66][verification needed][67][non-primary source needed][68][non-primary source needed]} In the period of April–May 1942, the communists established another military unit to struggle against Chetniks - Grmeč Anti-Chetnik Battalion, with 800 Partisans ordered to destroy Chetniks of Drenović, Vukašin Marčetić and Lazo Tešanović.^[69] The pressure of the Grmeč Anti-Chetnik Battalion forced Uroš Drenović to sign an accord with representatives of the Independent State of Croatia on 25 April 1942.^[70]

In post-war Bosnia and Herzegovina, 27 July was celebrated as public holiday in honor of the uprising of the people of Bosnia and Herzegovina, completely ignoring the much earlier June uprising in eastern Herzegovina.^[71] The monument in honor of the uprising in Drvar, constructed by sculptor Marijan Kocković, was erected in Drvar.^[72] In 1996 the Croatian Army destroyed the monument designed by Kocković and it was never rebuilt.^[73]

In 1988 Božidar Sokolović published a book in honor of Ilija Desnica, one of the leaders of the uprising, titled Ilija Desnica: The Hero from Oštrelj.^[74]