Francetić earned his only military education and officer rank while serving in the Royal Yugoslav Army. He became a non-commissioned officer in the rank of sergeant. Regarding Francetić's military experience and knowledge, Eugen Dido Kvaternik wrote: "He did not have basic military knowledge and military education, nor did he have any talent for basic military organization." After establishment of the Independent State of Croatia in April 1941 Francetić and 10 others organized the Black Legion. Francetić became the leader of the Black Legion and earned the rank of colonel in the Ustaša army. Kvaternik believed Francetić "a born guerrilla and a son of our mountainous Herzegovina", which was sufficient reason to elevate him to military leader in Bosnia and Herzegovina.