The Cold War turned East Africa into a battleground both figuratively and literally, for it was the site of sharp competition for influence between the US and the Soviet Union as well as the site of many proxy wars (wars fought by other countries with the combatants backed by the US and the Soviet Union).
As the rivalry between the US and the Soviet Union (and between their respective political systems) grew throughout the Cold War period, each country sought to gain influence over other, smaller, less powerful countries. If they could install rulers in these countries with a political philosophy that matched their own, they could develop important allies throughout the world. East Africa did not escape this attempt. At this point, many African countries were fighting for their independence after generations of colonization, and the US and Soviet Union were quick to step up with financial aid, weapons, political advice, and their own candidates for an independent government. The two superpowers thereby pitted factions against each other in developing countries, each hoping to come out on top.
In Somalia, for instance, the Soviet-supported General Mohamed Siad Barre came to power and established a communist government (with Soviet funding, of course). In Ethiopia, Emperor Haile Selassie was overthrown by a communist regime as well.
Often, in the midst of all this political competition, actual fighting broke out as the Soviet- and US-backed factions descended into proxy wars. Often, the superpowers actually supported the combatants with troops, weapons, money, or some combination thereof. Other times, though, one superpower, usually the US, decided not to intervene in a conflict even though this, too, was a political statement. In Somalia, Barre ended up fighting against Ethiopia, and the Soviets decided to support the latter. Barre called on the US for support, renouncing his ties to the Soviets. The US provided some money but did not send military support, and the Somalis lost what came to be known as the Ogaden War.