In Nigeria, Britain asserted its post-colonial security role during and immediately after the transfer of power, and remained responsible for assisting the Nigerian armed forces. While the Americans recognized Nigeria's potential as an important partner in the Cold War, they preferred to focus on development aid. Washington was thus supposed to complement British assistance, while leaving the responsibility for the security sector to London. But with the escalation of the Cold War in Africa, the Nigerians' efforts to reduce their dependency on the United Kingdom, and Nigeria's growing significance for the United States in African affairs, this Anglo-American burden-sharing was increasingly questioned in Washington. The United States thus eventually decided to militarize its aid policy towards Nigeria. In analysing the militarization of US aid policy towards Nigeria, this article will, first, assess the Anglo-American relationship in the early 1960s; secondly, position Nigeria in American Cold War policy towards Sub-Saharan Africa; thirdly, question the role of military assistance in Washington's policy towards Nigeria and Africa; and fourthly, discover the regional and local factors that influenced policy-makers in Washington and London.