Haile Selassie, in his decree in 1944, prohibited missionaries from attempting to convert Ethiopian Orthodox Christians, and they had little success in proselytizing among Muslims.
During the time, the focus of most missionaries was on adherents of local religions–but still with only small success. In the 1960s, there were about 900 foreign missionaries in Ethiopia, however many were layperson.
One obstruction to the missions’ achievement in the rural areas may have been the imperial government’s insistence that Amharic be used as the medium of religious instruction except in the earliest stages of missionary activity.