Since antiquity, diplomacy has always been a constant in relations between human societies. By the eighteenth century, it had assumed most of the features of its modern form. Initially a European creation, the modern diplomatic system gradually expanded to the rest of the world. Multilateral diplomacy received a major boost by the two World Wars. New institutions, new functions, and functionaries have been introduced. Diplomacy has been decisively affected by the historical process although in its main features it remains unchanged.