A member of the Illyrianist People's Party, he supported the independence of Croatia from the Austrian Empire.

[3] In September 1843 Tadija enrolled at the Greek Catholic Seminary in Zagreb, where he would stay for nine years.

He was a member of the Independent People's Party, and was a follower of Franjo Rački and bishop Josip Juraj Strossmayer.

In the 1886/87 academic year he became the dean of the Faculty of Philosophy and soon after was selected as the rector of the entire university.

Smičiklas published the first history of Croatia (2 volumes, 1879–1882) which was scholarly, critical, comprehensive and founded on reliable authenticated evidence that, together with his other work, laid the foundation for Croatian scholarly historiography and contributed to the strengthening of the idea of continuity of Croatian statehood and independence.