did he later become the head of state?
His official title was Chairman of Derg, and he held the position of Head of State in an acting capacity
Aman Andom
Aman's official title was Chairman of the Provisional Military Administrative Council (better known as Derg), and he held the position of Head of State in an acting capacity as the military regime had officially proclaimed Crown Prince Asfaw Wossen as "King-designate" (an act that would later be rescinded by the Derg, and which was never accepted by the Prince as legitimate).

where is mogadishu located? Somalia how does the place get its name? Somali word "Muuq Disho" and the Arab-Persian word "Maq'ad-i-Shāh" can you mention any one sultanate that ruled this place? Mogadishu Sultanate can you name any ruler from it? Fakhr ad-Din was this place ever colonized by any foreign power? Yes, Italian colonialism why was the civil war fought? Barre's regime had become ever more totalitarian, and resistance movements, encouraged by Ethiopia's communist Derg administration, sprang up across the country. can you tell a little more about this administration that you referred to? It was officially the Provisional Military Government of Socialist Ethiopia, refers to the military junta. when was it formed? June 1974 who was the founder? Low-ranking officers of the Ethiopian Army and police led by Chairman Aman Andom. was this chairman too a part of the military? Yes
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Aman Andom [SEP] Head of State
At the same time, this group of soldiers assumed the name "Provisional Military Administrative Council" ("Derg"). From the first day of his presidency, the Ottaways note, "the general found himself at odds with a majority of the Derg's members over most major issues, including whether he was chairman of the ruling military body or simply its spokesman. Aman fought the majority of the Derg over three central issues: the size of Derg, which he felt was too large and unwieldy; the policy to be taken towards the Eritrean Liberation Front (ELF); and over the punishment of the numerous aristocrats and former government officials in Derg's custody.