For a brief moment in the late-1950s, British policymakers and key African politicians shared a vison: an East African Federation of Kenya, Tanganyika, and Uganda. For British officials, one of the leading advantages would be transforming the colonial King’s African Rifles into a federal army. This aspect of the plans has rarely been recognised, but this article shows that British planning for the KAR became inextricably intertwined with federal thinking. Late colonialism was a time of alternative federal visions in addition to increased interventionism as British officials foresaw the end of colonial rule and sought to remake African institutions. A federal army was a key aim in such plans. This article argues that although no federation or federal army came into being, planning for them substantively shaped the military inheritance of the region at independence. Uganda and Tanganyika achieved independence with armies that were not fully autonomous, while Kenya took most of the shared colonial facilities. Thus, the article highlights the impact late colonial plans could have even when these did not come to fruition.