He graduated from the Military Academy of the General Staff School. He became State Secretary of Military Matters of Serbia in 1902. As President of the National Defence, he participated in the Chetnik fighting for Macedonia.
In World War I he was the Chief of Staff of the Montenegrin Supreme Command until June 1915 and a delegate of the Serbian Supreme Command at the Montenegrin Supreme Command.
Janković died on 7 July 1920 in the town of Herceg Novi.[2] The town of Elez Han in Kosovo was named 'Đeneral Janković' after him.
His son Milojko B. Jankovic (1884 - 1973) was the army general in the army of the Kingdom of Yugoslavia.