Nikola Kalabić (Serbian Cyrillic: Никола Калабић; 20 December 1906 – 19 January 1946) was a Serb and Yugoslav surveyor and Chetnik commander during World War II.

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.

During World War II, Nikola Kalabić was commander of Draža Mihailović's formation named the Mountain Guard Corps (Serbian Cyrillic: Корпус горске гарде).

[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.

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.

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.

[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.

[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.