During the 1998-2000 War Ethiopia, as well as Eritrea had allies. While the war took place, a regional destabilization was caused as a result of it. So when the war started to spread to Somalia both countries look for allies.
On one hand, Ethiopia allied with groups from the southern part of Somalia which were against Mohamed Farrah Aidid (a Somali warlord). Also, it teamed up with the Islamic Regime in Sudan and an Eritrean rebel group known as the Eritrean Islamic Jihad. While on the other hand, Eritrea teamed up with the Oromo Liberation Front.