Tokyo is quietly rewriting the rules of its external engagement. In 2023, Japan launched the Official Security Assistance (OSA), a bold new initiative aimed at supporting the defence capacities of like-minded partners across the Indo-Pacific. Unlike past frameworks centered on development alone, OSA marks Japan’s entry into the domain of security assistance, albeit within the boundaries of its pacifist constitution. As maritime tensions rise and regional power balances tilt, OSA represents a strategic recalibration: a blend of normative caution and realpolitik, designed to strengthen regional deterrence while preserving Japan’s commitment to peace.....