In 395 AD, Rome split into two empires - the Western Roman Empire and the Eastern Roman Empire. Each side had a ruler in charge of it. The Roman Empire was split by Theodosius.
The First Geneva Convention (1864) is one of the earliest formulations of international law. International law is the set of rules generally regarded and accepted as binding in relations between states and between nations. It serves as a framework for the practice of stable and organized international relations.
The rules of international law do not cover all aspects of the relations between the states. International Law overlaps with the Foreign Relations Law to the extent that the domestic law of the United States includes rules giving effect to rules of international law, but does not cover the same subject matter.