This chapter briefly reviews the organizational structure of North Atlantic Treaty Organization (NATO), its history, and evolution in membership. The theoretical lenses in the chapter, focus on the case study of the Ukraine to highlight the differing perspectives regarding the role of NATO in regional security governance. The North Atlantic Council (NAC) provides the highest levels of leadership for NATO. NATO shapes contemporary international relations through its expansion. At the same time, international relations also shape NATO. The chapter examines a multipurpose regional intergovernmental organizations (IGO), the Economic Community of West African States (ECOWAS), in terms of its structure and its role in West African security. ECOWAS leadership in peace and security operations ranges from being the first to react and respond, to remaining engaged in the rebuilding process after global attention has waned. The revised principles of ECOWAS guard against coups and establish democracy as a preferred mechanism for selecting the legitimate heads of state/government.