Complex sentence: The Ethiopian Navy contributed nothing to Ethiopias victory over Somalia in the Ogaden War of 1978, and Mengistu increasingly began to divert resources from the navy to the Ethiopian Army and Ethiopian Air Force, and the Ethiopian Navy began to decline further in its capabilities.
Split into simpler sentences: The Ethiopian Navy contributed nothing to Ethiopias victory over Somalia in the Ogaden War of 1978, and Mengistu increasingly began to divert resources from the navy to the Ethiopian Army and Ethiopian Air Force. As a result, the Ethiopian Navy began to decline further in its capabilities.