In 1943, the Japanese Occupation Government formed the Defenders of the Fatherland Army an auxiliary force consisting of Indonesians which were designed to assist the Japanese should the Allies come to invade Indonesia. Like many of his military contemporaries, Panggabean joined. In Panggabean's case however, he seemed to have only manage to go through military schooling and basic training before the Japanese surrendered and nationalist leaders Sukarno and Mohammad Hatta proclaimed Indonesia's independence.