The idea and practice of establishing foreign military bases in the Horn of Africa (HoA) is an enduring phenomenon. The Cold War ideological and geopolitical rivalry between the US and the Soviet Union in Africa was largely played out in the HoA through proxy states. The region's geopolitical and strategic significance had been diminished by the end of the Cold War and with the withdrawal of the two superpowers’ military bases. Foreign powers' intervention in the HoA in the 1990s was dominated by humanitarian intervention and multilateralism. Yet, the number, diversity, and motives of external powers involved in the region, through establishing military bases or maintaining a semblance of security presence in the post-9/11 period, are unprecedented. One consequence of September 11 is that the region has become increasingly militarized and securitized under the banner of the war against terrorism. The central aim of this study is to explore the expanding overseas foreign military bases in the core HoA region and their implications for the region and, in particular, Ethiopia’s security. The research design addresses the objectives by using a qualitative research approach and a case study design. The data sources included interviews with analysts, experts, researchers, and officials from various security and security-related institutions and were supplemented with document analysis. Among the external powers deeply involved in the HoA, the US, China, and the Gulf States are selected as cases. To understand the crux of the new geopolitics of foreign military bases in the HoA, the realist and constructivist traditions, primarily the regional security complex theoretical frameworks, are utilized. Power politics and unilateralism heavily influenced the geopolitical developments in the past and continue to do so today. The proliferation of multiple non-African powers (from superpowers to regional and small powers) and security structures from different parts of the world into the Horn subregional security complex signifies the utility of regional security complex theory for this study. The underlying reason for the recent expansion of overseas foreign military bases in the region was the threat of international terrorism and piracy. This study reveals that the role of foreign military bases is shifting to geostrategic dimensions, thereby signaling the return of great power rivalry. The region once again has become a playing ground for intense Sino-US and Middle Eastern states' competition. The rivalry and contestations of external powers have heavily impacted intra- and inter-state interactions and the geopolitical and security landscape of the HoA. Such global and regional geopolitical developments exert enormous pressure (economic, political, security, and strategic) on Ethiopia, an anchor state in the region. Although largely reactive, Ethiopia has embarked on subtle policies in response to the geopolitical dynamics of the presence of the foreign military bases in the subregion.