ver the years Haile Selassie I ruled Ethiopia, Aserate held several positions including Governor of Arsi, and of Shewa. He was the president of Ethiopian Senate from 1961 to 1964. In 1964, he was appointed Viceroy of Eritrea. His chief rival was Prime Minister Aklilu Habte-Wold. The rivalry between the two prominent figures was caused by the suspicions between the conservative court faction made up largely but not exclusively of the nobility and church hierarchy, and led by Prince Aserate, and the faction of reformers led by the commoner technocrats led by the Prime Minister and officials largely of humble birth that owed their education and appointment to positions of power to the Emperor.
In 1966, Aserate Kassa was raised from Dejazmach to Ras. His elevation followed the death of his father Leul Ras Kassa, and his assumption of the headship of the Selalle line of the dynasty.
Ras Aserate struggled with the growing unrest in Eritrea. One part of his response was to create two armed groups under his direct control and funding: a commando force made primarily of Christian Eritreans and trained by the Israelis, and an Eritrean security force. The other part was to engage in discrete negotiations in hope of reconciling most of the populace based on appeals to shared highland Christian heritage.