He was a member of several Yugoslav academies of sciences and arts, the author of more than a dozen historical books, and received several significant national awards.

This involved local historians eschewing the standards of international scholarship and concentrating exclusively on sectarian myths, resulting in the production of what has been described in historiographical assessment of the period as "pseudohistory".

Ekmečić added a religious flavour to this by claiming that the Vatican was an enemy of the Serbian nation, and also that it posed the biggest obstacle to Yugoslav unification in 1918.

[1] When the Kingdom of Yugoslavia entered World War II due to the Axis invasion of the country in April 1941, Ekmečić remained in the Čapljina area until 1943.

On 6 August 1941, the ruling Ustaše perpetrated the Prebilovci massacre, in which Ekmečić lost 78 members of his family, including his father and uncle.

He received his doctorate in history from the University of Zagreb in 1958 upon defending his dissertation entitled The uprising in Bosnia from 1875 to 1878, which has been published in three editions and translated into German.

[7] The book was hailed as "one of the most comprehensive histories of Yugoslavia in the English language",[6] despite a tendency towards Marxist historiography and the absence of a detailed examination of the post-World War II period.

Instead, Ekmečić asserted that unitarian assimilation was to be preferred, saying that nationhood based on language was the only concept which was acceptable from both a rationalist and romanticist perspective.

According to the Croatian-American historian, Ivo Banac, Ekmečić's approach betrayed a double-standard, whereby he criticised only non-Serb South Slavic nationalism.

[1] Shortly after the outbreak of the Bosnian War in 1992, Ekmečić was arrested by the Bosnia and Herzegovina government-loyalist Green Berets paramilitary unit along with his family.

Initially held at the elementary school in Vratnik, he was then transferred to house arrest, from which he managed to flee to the Bosnian Serb-controlled proto-state known as the Republika Srpska.

[19][20] In a book published by the Serbian politician and academic Uroš Šuvaković in 2011, Ekmečić was quoted as saying that he was "not eager to be a member of the Serb Democratic Party, [but] was in the closest circle in which it was conceived".

[24] In the early 1990s Ekmečić spoke about "German Europe", which he said was dominated by an "invasion of clericalism", while in 1992 he claimed that the war in Bosnia and Herzegovina was a "new Serbian struggle" and a continuation of the "work that the Serbs began in 1804 by expelling the Turks from Serbia".

He recalled that during the negotiations, Ekmečić described the plan of the SDS regarding the formation of a single Belgrade-controlled "new Yugoslavia" created from all regions claimed by Serbia.

[5] This trend involved local historians eschewing the standards of international scholarship and concentrating exclusively on sectarian myths, resulting in the production of what has been described by several scholars of the period as "pseudohistory".