Simbolon entered
Giyūgun (義勇軍
giyūgun, voluntary army) training during the
Japanese occupation, and afterward graduated as a Second Lieutenant. He was later assigned to the
Gyugun battalion headquarters in
South Sumatra, in the education and training section. Immediately after the
Proclamation of Indonesian Independence,
People's Security Army (TKR) was formed and he was appointed Commander of the Palembang Ulu Division, with the rank of Colonel. In a reorganization of TKR forces in Sumatra, Simbolon was appointed Commander of Division I / Lahat (1945–46), who supervised 4 regiments and 15 battalions in South Sumatra. When TKR was changed into the Republic of Indonesia's Army (TRI), Simbolon became Commander of the Garuda VII Division in South Sumatra, which oversaw
Lampung,
Bengkulu,
Palembang, and
Jambi. During the
Second Dutch Military Aggression, the
Emergency Government of the Republic of Indonesia was formed in Sumatra, in which
A.K. Gani became military governor and Maludin Simbolon became the deputy. In 1950, he was appointed commander of the
Bukit Barisan Territorial-I Army Command, which was formed in conjunction with the formation of the North Sumatra Province which included
Aceh,
North Tapanuli,
South Tapanuli,
West Sumatra, and
East Sumatra. == PRRI involvement ==