Description
The maritime corridor connecting the South Atlantic to the Indo-Pacific has shifted from a residual category in middle-power strategic thinking to a primary axis of contestation and cooperation. Three structural changes drive this shift: reduced American willingness to underwrite global maritime security; instability across Middle Eastern trade routes that has revived the Cape Route as a primary trade corridor; and the consolidation of - licit and illicit - trans-Pacific flows linking South America to Asian markets. This paper asks how Japan, India, and Brazil can coordinate their maritime, defense-industrial, and supply chain security policies across this two-ocean corridor. Drawing on the concept of domain complementarity, the paper identifies four sub-domains where trilateral cooperation is feasible: sea-lane governance and maritime domain awareness, defense-industrial collaboration, counter-narcotics and transnational organized crime, and the protection of energy and critical minerals supply chains. South Africa, Australia, and the African littoral states figure as nodes on this corridor, while China's economic and maritime presence is treated as a structural condition shaping cooperation rather than a target of containment. The paper closes with policy proposals for advancing trilateral maritime cooperation.