Complex sentence: When the Derg gained control of Ethiopia, they shifted their source for the equipment, organisation and training away from Western European and American governments towards those of the Soviet Union and other Comecon countries, especially Cuba.
Split into simpler sentences: When the Derg gained control of Ethiopia, they lessened their reliance on the West. Instead they began to draw their equipment and their sources for organisational and training methods from the Soviet Union and other Comecon countries, especially Cuba.