He called for the end of the Austro-Hungarian rule in Bosnia and Herzegovina and annexation of the land by Serbia as a part of its access to the Adriatic Sea through Dalmatia.

Serbian prime minister Nikola Pašić directed Stojanović to contact émigré Croatian politicians Ante Trumbić and Julije Gazzari to form a body which would promote unification of South Slavs through expansion of Serbia.

Stojanović was a part of the Yugoslav Committee's delegation which negotiated and the signed short-lived Geneva Declaration defining the future common confederal state.

At the Paris Peace Conference (1919–1920), Stojanović was a representative of the newly proclaimed Kingdom of Serbs, Croats and Slovenes as an expert for Bosnia and Herzegovina.

In the summer of 1941, Stojanović started working for Mihailović in his Belgrade office and formally joined the Central National Committee in August 1943.

[3] Stojanović's article applied Social Darwinism to model Serbian approach to non-Serbs and became cited as the blueprint for ethnic cleansing by Croatian writers.

Josip Frank, the most prominent Croatian nationalist and leader of the Pure Party of Rights, collaborated with the Hungarian authorities and called his followers to streets.

The ensuing riots targeting Serb businesses and homes in Zagreb [sr] were welcomed by Frank and denounced by Radić,[9] as well as the entire Croatian opposition.

A substantial portion of the public interpreted the riots as a result of Habsburg and Hungarian efforts to ensure a dominant position in Croatia-Slavonia by preventing unity of Croats and Serbs.

[14] Serbian prime minister Nikola Pašić directed Stojanović, and a fellow-Bosnian Serb member of the Diet of Bosnia Dušan Vasiljević to contact émigré Croatian politicians and lawyers Ante Trumbić and Julije Gazzari with the aim of establishing a body which would cooperate with the government of Serbia on unification of South Slavs in a state created through expansion of Serbia.

[17] Stojanović took the position that if unification of South Slavs becomes impossible, in case of a negotiated end of the war, Serbia should capture Bosnia and Herzegovina to reverse Austro-Hungarian annexation of 1908 and to gain territory in Dalmatia as an access to the sea.

Stojanović voiced opposition, without specifying reasons, to the Corfu Declaration on unification signed by Pašić and Yugoslav Committee president Trumbić—affirming that the new union will be a monarchy ruled by the Karađorđević dynasty.

[25] At the Paris Peace Conference (1919–1920), Stojanović was a representative of the newly proclaimed Kingdom of Serbs, Croats and Slovenes as an expert for Bosnia and Herzegovina.

According to various sources, he was appointed one of its vice-presidents and/or a honorary member,[28][27] and he was in a group tasked with drafting the organisation's rules of procedure, as well as formulating its objectives.

In the summer of 1941, Stojanović started to work for Mihailović in his Belgrade office and formally joined the Central National Committee in August 1943.

[27] Later in 1943, Nazi German authorities in the Territory of the Military Commander in Serbia arrested him and took him to occupied France where Stojanović remained until the end of the war.