In 1917, he became disillusioned with the Karađorđević dynasty following the Salonika Trial, in which Vasić's cousin, Ljubomir Vulović, was sentenced to death and executed for being a member of the Black Hand.

Vasić participated in military exercises near the Albanian border and was later transferred to the 30th Infantry Regiment, which had been involved in suppressing an uprising in northern Albania.

[3] He began practicing law in Belgrade in 1921 and, in January 1922, represented a number of communist defendants who were accused of attempting to assassinate King Alexander.

[3] In 1922, he became close friends with Croat writer Miroslav Krleža, who regularly contributed to Vasić's magazine Književna republika (Literary Republic).

[5] By the time of King Alexander's royal dictatorship proclamation on 6 January 1929, Vasić was widely believed to be a communist sympathizer as a result of his dissatisfaction with post-war political developments in the Kingdom of Serbs, Croats and Slovenes.

[6] In 1931, he used his connections with General Petar Živković to secure the release of Đuro Cvijić, a former leader of the Communist Party of Yugoslavia who had been sentenced to death by authorities.

[9][10][11][12] He sided with Serbian nationalists during the concordat crisis in 1938 and opposed the Cvetković–Maček Agreement of August 1939, which granted greater autonomy to Croatia within the Kingdom of Yugoslavia.

[15] The Central Committee advised him on matters of domestic and international politics and maintained liaison with civilian followers of the Chetniks in Serbia and other regions.

[8] Historian Jozo Tomasevich notes that Vasić was "unsuited" to be the head of the committee, due to his "personality and lack of political experience".

For this reason, they cannot accept open collaboration of some of our commanders with the Germans and Italian troops, who have subjected them to unspeakable terror and atrocious crimes.

I am increasingly convinced that this open collaboration of our commanders with the Italian and German troops is the main reason for our defeats in combat with the Partisans, both militarily and politically.

[19] In February 1942, Vasić received a letter from Moljević concerning the creation of a Greater Serbia stretching to Dalmatia and the Adriatic coast.

He was particularly opposed to the political concepts laid out by Moljević and socialist politician Živko Topalović, stating: "I do not know why the Commander [Mihailović] needed this congress; I have to admit [it] was a circus of formality as far as I'm concerned.

"[23] In July 1944, Vasić and his wife met with Richard Felman and other American pilots, whose B-24 Liberators were shot down by the Germans near the Serbian village of Pranjani.

Vasić told him that they had recovered the body of a dead American pilot and assigned a young Chetnik named Miodrag Stefanović to be Felman's bodyguard.

[28] Đurišić had arranged for Dimitrije Ljotić's forces already in the Ljubljana Gap to meet him near Bihać in western Bosnia and assist his movement.

[29] In order to get to Bihać, Đurišić made a safe-conduct agreement with elements of the Armed Forces of the Independent State of Croatia (HOS) and with the Montenegrin separatist Sekula Drljević.

Following this defeat and the defection of one of their sub-units to Drljević, Đurišić was induced to negotiate directly with the leaders of the HOS forces about the further movement of the Chetniks towards the Ljubljana Gap.

[33] His first book, titled Karakter i mentalitet jednog pokoljenja (The Character and Mentality of a Generation), was published in 1919, shortly after the end of World War I.

A book titled Dva meseca u jugoslovenskom sibiru (Two Months in the Yugoslav Siberia) was published in 1920, shortly after he returned to Belgrade from military exercises on the Albanian border.

Upon returning from the Soviet Union in 1927, he wrote a book titled Utisci iz Rusije (Impressions From Russia), which was published the following the year.