Having originally earned his officer's commission with the Republic Army, Thedus Bimm served with the 83rd Assault Division before applying for the Inter-Service Training School in order to join the Republic Marines. By the time of the Republic's involvement in the Mandalorian conflict, he had been posted to the 3rd Marine Battalion's Besh Company, which had recently been placed under the command of Laera Reyolé. During the war, he fought with savage bravery, once having decapitated a Mandalorian warrior who had been clad in full assault armor.