Short answers, pulled from the story.
The Chetniks carried out mass killings, forced expulsions, and the destruction of villages, mosques, and Catholic churches, primarily against Muslims and Croats in Bosnia and Herzegovina, Herzegovina, and Dalmatia. They also executed captured Partisans, attacked Partisan field hospitals, and killed Jews hiding in Serbia. Most historians who have studied the record regard the crimes against Muslims and Croats as genocide.
Estimates vary widely. Demographer Vladimir Žerjavić put the toll at 65,000 to 68,000 Muslims and Croats across different studies, while researcher Rudolph Rummel's estimates ranged from 50,000 to 500,000. Historian Šemso Tucaković estimated around 100,000 killed.
Colonel Draža Mihailović led the Chetniks after refusing to surrender following Yugoslavia's capitulation in April 1941. He was captured on the 13th of March 1946, convicted of war crimes and high treason, and executed on the 18th of July 1946 along with nine other Chetnik commanders.
The genocidal campaign reached its peak between October 1942 and February 1943, including the Operation Alfa killings near Prozor and commander Pavle Đurišić's operations in Sandžak, where around 8,000 women, children, and elderly people were reported killed in February 1943 alone.
Yes. The Chetniks executed captured Partisans, including handing 350 prisoners to the Nazis in November 1941, and repeatedly attacked Partisan field hospitals, killing wounded patients and nurses in locations such as Jastrebac and Semberija in 1944.
No, historians remain divided. Scholars such as Jozo Tomasevich and Marko Attila Hoare describe the Chetnik campaign against Muslims and Croats as genocide, while David Bruce MacDonald has disputed that characterization, arguing there is no concrete evidence of intent to exterminate the Croatian population.