Which one of the following pairs of countries fought wars over a region called Ogaden ?

The Ogaden was the theater of a major interstate conflict between Ethiopia and Somalia in 1977–78, when Somali forces and allied guerrillas sought to annex the predominantly Somali-inhabited Ogaden region of eastern Ethiopia. Somalia invaded and occupied large parts of the Ogaden in 1977, triggering a war often called the Ogaden War; Ethiopia ultimately regained the territory with substantial external assistance, and Somali forces were expelled by early 1978. Historical and encyclopedic accounts explicitly identify the Ogaden War as a war between Ethiopia and Somalia over that region, distinguishing it from other Horn of Africa border disputes involving neighbouring states [1].

Sources

1. [1] https://www.britannica.com/place/Ogaden