Mare Dominium: Effective Maritime Control and the Transformation of the Freedom of the Seas

History has not yet recorded the conquest of the seas. For centuries, the freedom of the sea rested not only on legal doctrine but on a material fact: the sea could not be occupied and held like land. Mare Dominium asks what follows when that material limit begins to weaken. The article makes one central distinction: legal sovereignty and effective maritime control are not the same, and the second can expand without the first. It traces that problem from Mare Liberum and Mare Clausum through the growth of coastal-state jurisdiction, Freedom of Navigation Operations and the integration of satellites, artificial intelligence, unmanned systems and long-range intervention. The Strait of Hormuz is used as the principal contemporary stress test. Mare Dominium does not mean sovereignty over the high seas, nor the disappearance of Mare Liberum. It describes an emerging condition in which the legal boundary may remain fixed while the effective reach of power moves outward. The article then carries the argument into the Eurasian-Atlantic strategic balance, presents the Türkiye-Russia-China-Iran (TRÇİ) alliance proposition developed in Denizlerin Fethi Çağı, and extends that proposition into the maritime domain by arguing for increasingly coordinated practices at sea.