Franjo Šimić was born on 25 May 1900 in Gospić, a town in Kingdom of Croatia-Slavonia, a part of the Austro-Hungarian Empire.

Šimić returned to the infantry regiment of King's Guard, this time serving as a commander of a company until 18 March 1930 and while in that position he rose to the rank of kapetan.

[d][2][5] On 6 April 1941, Axis powers invaded Yugoslavia, at that time Šimić was commander of a VI subsection of the border troops.

On 6 July, Šimić issued an order in which he established rules of behavior and "most strongly forbid terror, violence, pillaging and any mess".

[9][10] Šimić became a commander of the Home Guard Nevesinje Brigade which conducted counterinsurgency operations in eastern Herzegovina against a new uprising that begun in mid-August 1941.

[14][15] In early July 1942, Šimić arrived in Bugojno to organize defences in that area where an attack by Yugoslav Partisans was expected.

He was awarded the Military Order of the Iron Trefoil III Class in late 1942 for his role in the defense of Kupres and Bugojno.

He was allegedly assassinated in Mostar in 1944 and posthumously awarded the Military Order of the Iron Trefoil II with Wreath, which gave him the title of vitez (knight).