when did the leader join the military?
October 1910.
Draža Mihailović
 Mihailović himself joined the Serbian Military Academy in October 1910. 
what is ba congress? It was a meeting of representatives of Draža Mihailović's Chetnik movement between 25 and 28 January 1944 in the village of Ba in the German-occupied territory of Serbia during World War II. what was its objective? It  aimed to advance a political alternative to the November 1943 Second Session of the communist-led Anti-Fascist Council for the National Liberation of Yugoslavia (, AVNOJ) of the Yugoslav Partisans. who were it participants? They were from Serbia, Montenegro and Bosnia together with two or three Croats, one Slovene and one Bosnian Muslim.
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Draža Mihailović [SEP] Early life and military career
Dragoljub "Draža" Mihailović was born on 27 April 1893 in Ivanjica, Kingdom of Serbia to Mihailo and Smiljana Mihailović ("née" Petrović). His father was a court clerk. Orphaned at seven years of age, Mihailović was raised by his paternal uncle in Belgrade. As both of his uncles were military officers, Mihailović himself joined the Serbian Military Academy in October 1910. He fought as a cadet in the Serbian Army during the Balkan Wars of 1912–13 and was awarded the Silver Medal of Valor at the end of the First Balkan War, in May 1913. At the end of the Second Balkan War, during which he mainly led operations along the Albanian border, he was given the rank of second lieutenant as the top soldier in his class, ranked sixth at the Serbian military academy.