This chapter investigates how the Italian trusteeship over Southern Somalia (Amministrazione Fiduciaria Italiana della Somalia – AFIS) affected both Somalia’s reunification and its following social and political troubles. AFIS was a peculiar case among the United Nations (UN) Trusteeship System since Italy was not a UN member yet and because it was a trustee over a territory that once was its former colony. When the Trust Territory of Somaliland was reunited with the former British Somaliland in 1960, it became evident how different approaches to governance between Rome and London affected relations among Somali clans, de facto laying the foundations for future instability. As this chapter establishes, not only does the Somali case represent a clash between two different “civilizing missions” of Western countries, but also it reveals how the Italian and British governments encouraged the emergence of distinct visions for Somali nationalism. In particular, the AFIS imposed an Italian way to “Somalization,” which contributed to the destabilization of the socio-political panorama of the country. In that sense, the case of the Trust Territory of Somaliland offers an emblematic example for the failure of the UN supervision over African decolonization, the problematic legacy of which starkly manifested in recent decades.