Taking place between July 1977 and March 1978, the Ogaden War between Somalia and Ethiopia was a territorial conflict over the then disputed Ogaden region located in between both countries.
With both countries claiming ownership over the region, things took a downward spiral somewhere around July 1977 when Somali forces launched a military offensive in Ethiopia. Keep in mind that the Cold War between the United States and the Soviet Union was also ongoing at that time.
With the Soviet Union not in support of the invasion, they cut ties with Somalia and rather supported Ethiopia. The United States, on the hand, also cut ties with Ethiopia and started supporting Somalia.
With massive support from Cuba and other allies, Ethiopia managed to push the Somali forces out of Ogaden. The aftermath of the war left a huge number of the Somali Army invasion forces killed and about half of their airforce destroyed. The effects of this war brought about unrest and anger in Somalia and instigated the Somali civil war.
Below are some photos of the Ogaden War: