What countries make up the Horn of Africa?

This is the peninsula that juts out from the northeastern corner of the African continent into the Arabian Sea and the Indian Ocean, shaped roughly like a rhinoceros horn pointing eastward, which is where the name comes from.

Ethiopia is the landlocked giant of the group, the most populous country in Africa after Nigeria, and the seat of the African Union. Eritrea sits along the Red Sea coast to Ethiopia's north, and the two countries share a fraught history, having fought a brutal border war before a peace deal was finally reached. Djibouti is tiny but strategically significant out of all proportion to its size, sitting at the mouth of the Bab el-Mandeb strait, the narrow waterway through which a significant share of global shipping passes on its way between the Red Sea and the Gulf of Aden. Somalia occupies the tip of the horn itself, stretching down the Indian Ocean coastline.

Some analysts extend the definition to include Sudan, South Sudan, and Kenya, calling it the broader Horn or the Greater Horn, but the core four are the ones almost every definition agrees on.

Why this connects to what we were discussing

The Horn matters enormously to the US embassy building picture. Djibouti hosts Camp Lemonnier, the only permanent US military base on the African continent. China has its own military base there too, literally within sight of the American one. Ethiopia, as the AU's home, is one of the most diplomatically consequential posts on the continent. Somalia has been a focus of US counterterrorism operations for years. This is not background geography. It is some of the most actively contested ground in the US-China competition for influence in Africa that the embassy building program is directly responding to.