With fascist Italy's help, the Chetniks established a form of civil and military government in large parts of eastern Bosnia, which was followed by discriminatory measures and systematic massacres of non-Serbs in the region.

The leader of one such organization was Puniša Račić, who in 1928 killed two deputies of the Croatian Peasant Party (HSS) and mortally wounded its president, Stjepan Radić, in the Yugoslav Parliament.

These organizations were dissolved following the imposition of royal dictatorship by King Alexander in 1929, and most of their members moved to the original "Chetnik Association for Freedom and Honor of the Fatherland" that continued to function.

[9] The Chetnik subcommittees and organizations with a similar program opposed the formation of the autonomous Banovina of Croatia, that was negotiated in August 1939 under the Cvetković–Maček Agreement by Croatian and Serbian political leaders.

[27] The majority of documents of the Chetnik leadership emphasized "cleansing", "resettling", or "moving" of non-Serb populations, as well as the executions of "traitors", which turned into mass killings of Croats and Muslims.

[45] The leaders of those groups, among whom were former politicians, former officers of the Yugoslav Army, and Orthodox priests, were affiliated to pre-war nationalist organizations or local subcommittees of the Chetnik Association.

Houses in Bosansko Grahovo and in the surrounding villages of Obljaj, Korita, Luka, Ugarci, and Crni Lug were burned and over 250 Croat civilians were killed in these attacks.

[52] Victims of the massacres in Kulen Vakuf (which included hundreds of women and children) were shot, stabbed, hacked to death with axes and other farm tools, or drowned in the river Una.

[75] Todorović established contacts with the Italians and negotiated the transfer of control of parts of eastern Bosnia, the Foča, Goražde, and Višegrad districts, to the Chetniks in November 1941.

The Italians compelled the NDH authorities to withdraw from these areas, and then turned it over to the Chetniks, who established their own civil and military government called "Provisional Administration of East Bosnia".

[77] Dangić gave a speech in Goražde, made references to a Greater Serbia, and concluded that "we cannot be together anymore, we and the balije [a vulgar term used against Bosniaks as well as those that identified as Muslims within the Balkans]."

[86] During a June 1942 conference of Chetniks in the Manjača region in Bosanska Krajina, local commander Vukašin Marčetić declared his hope that "Bosnia will be cleansed from everything that is not Serb.

[98] Baćović described their activities during Operation Albia and spoke openly of their efforts to exterminate or cleanse the Croat and Muslim populations, and cited examples of burning of villages and killing of civilians in the area of Ljubuški and Imotski.

Chetnik forces massacred Croats and Muslims and burnt numerous villages in Prozor, before they were ordered by the Italians to leave the area on the insistence of the NDH government.

[126] The military defeats suffered at the hands of the Partisans in March and April 1943, German harsh measures, and the loss of influence in the government-in-exile, had a serious impact on Chetnik activities.

[131] On 10 July 1943, Đujić Chetniks and members of the Italian "Bergamo Division" massacred more than 112 Croat civilians and captured Partisans in the village of Lovreć and surrounding areas.

[133] On 30 April 1944, Chetniks, in collaboration with the SS Police Regiment Bozen and local Italian Fascists, massacred 269 Croat civilians in village of Lipa, near Rijeka, of whom 121 were children between seven months and 15 years old.

[153] The Chetniks slaughtered dozens of captured Partisans,[154] including renowned Croatian poet Ivan Goran Kovačić,[155] during the Case Black operation in June 1943.

They initially hid in the basements with fifteen nurses for ten days after Operation Morgenstern, a joint anti-Partisan offensive of the Wehrmacht, NDH forces and Chetniks in Lika.

In the summer of 1942, Montenegrin Chetniks, under the command of Blažo Đukanović, Bajo Stanišić and Pavle Đurišić (with the approval of Mihailović), cooperated fully with Italian forces during the period of anti-Partisan terror and reprisals against suspected collaborators, across large areas of occupied-Montenegro.

After they signed a ceasefire-and-cooperation agreement with the Nazis in the region on 26 November 1943, Chetniks brought their units and began to clear the area.All areas close to Belgrade are infested with communists and their supporters.

[166] Vladimir Geiger of the Croatian Institute of History in Zagreb notes that research into human losses of Croatia and Yugoslavia during the Second World War (and in the immediate post-war years) is a controversial task and remains a sensitive political topic.

[169] The historian Sabrina P. Ramet also cited that figure, and wrote that the Chetniks completely destroyed 300 villages and small towns and a large number of mosques and Catholic churches.

[119] Živko Topalović, who was a close associate of Mihailović and president of the 1944 Ba Congress,[176][177] claimed that the Chetniks had killed as many as 40,000 Muslims from Bosnia, Herzegovina and Sandžak by January 1944 alone.

[179] For the territory of Sandžak in Serbia and Montenegro, the researcher Safet Hadžibegović published a victim list of 3,708 Muslims of the Priboj District that were killed by the Chetniks, mostly in early February 1943.

[182] According to the Yugoslav government's "State Commission for the Determination of Crimes Committed by the Occupiers and their Supporters", the Chetniks were responsible for the deaths of 8,874 Serbian citizens outside of fighting, and the burning of 6,828 buildings.

Public prosecutor Miloš Minić accused Lukačević of a massacre in Foča as commander of Chetnik units in Bosnia, participation in the extermination of the Muslim population, collaboration with the Nazis and Milan Nedić, and of crimes against Yugoslav Partisans.

Moreover, Bećirević cites the work of historian Max Bergholz who through his research found that many of the former Chetniks who participated in the massacres of Muslims were later absorbed into the Partisan movement and thus were not persecuted after the war ended.

[79] Michele Frucht Levy explained that the Chetniks, without a state apparatus, a territorially united leadership and a media propaganda network, carried out ethnic cleansing and massacres, rather than genocide.

[204] On the other hand, historian Mark Levene also comparing the two movements noted: "what makes Chetnik genocidal violence so compelling is that it was achieved with even less coordination than the Ustasha could muster, almost as if its commanders knew what was expected of them.