He was born to father Milan and mother Joka in Podnovlje (municipality of Doboj) in present-day Bosnia and Herzegovina. He had a sister named Angelina (1912–1999).
Nikola's father separated from Joka after World War I and proceeded to get married three times. Nikola lived with his father at first so he attended school in places where his father served with the Serbian army. He eventually finished six grades of gymnasium before becoming a student of geodesy in Belgrade. During his studies, he met Borka (a year younger than him) who was born in Rajkovići near Valjevo in present-day Serbia into a family of old supporters of the People's Radical Party and Nikola Pašić. Borka and Nikola married in 1929 and on 3 August 1930 they had twins Mirjana and Milan. Their first service was in Belgrade. They then moved to Aranđelovac and finally back to Valjevo (where there are Kalabićs today). Nikola Kalabić (until the start of World War II) worked in Land-registry management in Valjevo.
World War II
During World War II, Nikola Kalabić was commander of Draža Mihailović's formation named the Mountain Guard Corps (Serbian Cyrillic: Корпус горске гарде).[2] On 26 November 1943, together with the General Inspector of Chetnik Troops Colonel Simić, he concluded a formal collaboration agreement (German: Waffenruhe-Verträge) with the representative of the German Military Commander in Southeast Europe, General der Infanterie (Lieutenant General) Hans Felber.[3]
As part of terror against Partisans and their supporters, Kalabić's Chetniks during period between December 31, 1942, and April 1943 killed with cold weapons 28 people from villages near Valjevo and Kosjerić.[4] Anonymous officer from Mountain Guard Corps wrote letter to Draža Mihailović on November 8 complaining that terror has gone so far that people are more afraid of Chetniks than of Germans, Bulgarians and Albanians. As an example of this terror he claimed that Kalabić beat personally 3 men and a girl in village of Ljubičevac, all innocent, whom latter died as consequence of beating.[5] On November 26 Mihailović issued an order to Kalabić saying: Continue cleansing of communists whereever you hear them...cleanse without mercy.[6]
In the night of 25 December 1943, Chetniks under command of Nikola Kalabić killed a large number of civilians in village of Kopljare, near Aranđelovac. Out of 22 killed, 19 were Romani. In a letter to Draža Mihailović, Kalabić wrote: In Kopljere we caught while sleeping and slayed 24 active communists, out of which 20 were Gypsies, who admitted to be so-called jarugaši, at day they do their housework, but at night in action. I killed them all. There is no proof that any of victims were involved with KPJ or involved in any armed fights. Source of Ministry of Interior of quisling government has a more precise description of the massacre, as they mention murder of 22 civilians, 19 Romani, of which 15 male and 4 female. It also mentions that Chetniks burnt all Romani houses, as well as houses of two peasants whose family members were members of partisans.[7] Mountain Guard Corps under Kalabić committed similar acts of terror against pro-partisan population in central Serbia, including massacre in Drugovac, single largest Chetnik massacre in any Serb village.[8] During July and August 1944 Mountain Guard Corps led by Kalabić committed string of robberies and beatings in villages around Prokuplje and in Dešilovac they executed 5 villagers.[9]
On October 24, 1944, Kalabić's Chetniks from Ivanjica came to Sjenica where they joined other Chetnik units, as well as German forces, Muslim Militia and Serbian Shock Corps - the column that retreated towards Bosnia.[10] Kalabić's troops in December had to retreat to Kladanj due to Partisan win near Šekovići, where 110 Kalabić's men died and 40 were captured.[11] In letter to Chetnik High Quarters on December 27, Kalabić complained about small amount of reinforcement (around 300 men), as well as that units under his command lack ammunition.[11] In Chetnik dispatch from January 16 writes that Kalabić got significant supplies from Germans.[12]Yugoslav People's Army estimated on March 25 that joint Chetniks forces of Kalabić, Dragutin Keserović and Dragoslav Račić around 2000 men, following fighting them around Gradačac.[13] On May 10 or 11 Kalabić went alongside main Chetnik column with Mihailović towards Zelengora. Column size was estimated by Yugoslav Army to be around 3000 men.[14] Among captured Chetniks at Battle of Zelengora, where Chetnik main column was defeated, members of Kalabić's family(wife, daughter and mother-in-law). Wife and mother-in-law were sent back to Valjevo and daughter Mirjana by her own wish stayed in Yugoslav army until demobilization.[15] Kalabić was among few hundred fighters who escaped capture or death at Zelengora.[16]
On June 28, 36 Chetniks led by Kalabić and Filip Ajdačić crossed Drina to return to Serbia in Valjevo region.[17] Group of outlaws led by Kalabić appeared in November on territory of Yugoslav First Army killed 10 soldiers, 19 civilians and 1 policeman.[18]
Capture and alleged collaboration with the OZNA
Near the very end of the war, Kalabić and many other Chetniks tried to hide in rural areas of the country, awaiting an attempt to overthrow the new government. The OZNA had a plan to capture former members of the Chetnik movement and other military organizations outside of Yugoslavia. There, OZNA agents infiltrated the support network of Kalabić and arrested him in a covert operation on 5 December 1945.
After a few days, Kalabić agreed to collaborate with the OZNA in their efforts of locating and arresting Draža Mihailović, in return for immunity from prosecution. This claim however has been brought into question by family members of Kalabić claiming that he did not betray Mihailović. Kalabić was then executed by Yugoslav Partisans although this claim has also been questioned.[19]
Rehabilitation attempts
Kalabić was rehabilitated by the High Court in Valjevo in May 2017.[20] This decision however was overturned by an appellate court in Belgrade in May 2018.[21] On 7 August 2022, he was officially rehabilitated by the High Court in Valjevo.[22]