Between 1921 and 1925, Kun studied painting at the Royal Art School in Belgrade, where he was taught by painters Petar Dobrović, Ljuba Ivanović and Milan Milovanović.

During the next two years, he participated in spring and autumn exhibitions at the Cvijeta Zuzorić Art Pavilion in Kalemegdan, where the audience could see about a dozen of his compositions, portraits, still life paintings, self-portraits and landscapes.

The competition ended in November, and Kun's work under the title Crvena trojka (Red Triptych) was awarded the first prize of five thousand dinars.

Kun's interest in left-wing ideas and communism most likely arose during his stay in Paris, where he received books on Lenin and the Soviet Union from friends.

The conference of the International Association of Revolutionary Writers, held in 1930 in Kharkiv, and the First Congress of Soviet Writers, held in August 1934 in Moscow, defined the concept of socialist realism, an artistic style with the aim of spreading communist and socialist ideas, which highly influenced Kun's artistic output from that point onwards.

After returning to Belgrade, he created a set of graphics titled Blood-soaked Gold (Krvavo zlato) with the aim of displaying the lives of Yugoslav miners and workers.

With the help of architecture student Voja Midić, he reached printer Jovan Luks from Stari Bečej, who agreed to print the collection.

between May and June of 1937. students at the University of Belgrade organized a week of solidarity with the Spanish people, during which money was collected for the aid of volunteers leaving for Spain.

For the event, Kun painted the character of little Anita from Dušan Matić's poem Number 4-21-35 (Broj 4-21-35), which the student youth wore on their lapels.

He lived with his family in the house of his father-in-law Mihajlo Ratković at Kotež Neimar where he painted, collecting money for the publication of his graphics from Spain.

At the end of 1938, he managed to find a printer who printed the collection titled For Freedom (Za slobodu) in January 1939, which contained 12 graphics depicting the Spanish Civil War.

On the basis of the Decree, by which the Viceroyalty authorized the government to change existing laws and regulations instead of the dissolved National Assembly, as well as pass new ones.

Among those arrested were Moša Pijade, Ivan Milutinović, Ivo Lola Ribar, Bora Baruh, Blagoje Nešković and Kun.

Under pressure from the public and several prominent figures, the authorities of the Kingdom of Yugoslavia gradually released prisoners from the camp, which was officially abolished on 25 November 1940.

Construction of the house began in early 1941, but the bombing of Belgrade and the beginning of the occupation of Yugoslavia in April 1941 briefly interrupted the work.

[19] After the attack of the Axis Powers on the Kingdom of Yugoslavia and the bombing of Belgrade on April 6, 1941, Kun went to Bačka Palanka to report to the military command.

[21] Prior to the war, Kun learned how to create forged documents for the party, including passports, identification cards and stamps.

[22] With the help of his friend from Spain Milan Blagojević, who illegally lived in his house throughout 1939, he built his graphic press in the bunker's wall in May of 1941.

Sympathizers of the Partisan movement working for the Belgrade police, managed to hand over a copy of the German report to the KPJ leadership.

During the summer of 1941, Kun had a meeting in Belgrade with KPJ General Secretary Josip Broz Tito, whom he supplied with forged documents, but whose identity he did not know at the time.

[25] Since the beginning of the occupation, Kun lived in his cousin's apartment in Hadži Milentijeva Street, but due to the accidents that happened in the immediate vicinity in early August 1941, he had to change his place of residence.

At the suggestion of the Supreme Staff, and based on the decisions of the National Committee for the Liberation of Yugoslavia (NKOJ), he started working on the coat of arms and incorporated Moša Pijade's idea to use torches in the design.

During his stay in Jajce and later in Drvar, in the winter and spring of 1944, Kun worked together with Augustinčić on the creation of conceptual sketches for the first partisan awards established in May 1943.

At the suggestion of Ivan Milutinović, commissioner for the National Economy in the NKOJ, in April 1944, he produced the first partisan postage stamp in Drvar.

One of the works from the set is Kurir Jovica, which represents a boy-fighter with an oversized overcoat, boots and a stern facial expression, which over time became a graphic symbol of the youth of Yugoslavia in the War of National Liberation.

To create this sketch, Kun was helped by fifteen-year-old Jovan Tolomir, from the village of Podorugla, near Mrkonjić Grad, who was a courier of the Supreme Headquarters.

[29][30]After the liberation of Belgrade, the dean of the Technical Faculty under the German occupation, Branko Popović, was sentenced and executed as a national traitor by the new Yugoslav authorities in November 1944.

[31] In the official explanation of the verdict, it was stated that "Dr. Branko Popović, professor at the University and dean of the Technical Faculty" was "the closest associate of Minister Jonić," and as such, "denounced to Bećarević a number of freedom-loving students and citizens," who were subsequently sent to German camps, and that he also worked "on the fascistization of the Serbian people through the so-called Serbian Civil Plan.

"[31] Together with other defendants in the first post-war trial in Belgrade, the Military War Court sentenced him to "the death penalty, to be carried out by shooting, the permanent loss of civil rights, and the confiscation of all property.

In 1947, he obtained the title of master painter and held exhibitions in Belgrade (1953 and 1959), Kragujevac, Čačak, Niš, Skopje and Sombor, and in Berlin in 1963.