Joseph Story thought that the United States needed more than courts to vindicate its independence in the War of 1812. The youngest justice on the Supreme Court also believed that the nation needed legal doctrines that would support its aspirations to global power. For decades, American policymakers – and especially the Court under John Marshall – had defended the rights of neutral nations to trade peaceably in wartime. That approach made sense when a militarily weak but commercially vigorous United States sought to profit from trade with European powers embroiled in conflict. But now that the United States itself was at war, Story envisioned a different national future, in which a robust military and strong central government were the foundation of American sovereignty. The split that emerged on the Court over neutral and belligerent rights reflected a generational divide over how to preserve and extend American independence, and it fractured the Marshall Court’s prior unanimity. Despite Marshall’s resistance, Story persuaded his colleagues to adopt doctrines that favored the rights of nations at war, pushing the courts – and the country – to assume a more assertive presence at sea.