Diplomacy is a neglected aspect of Hellenistic history, despite the fact that war and peace were the major preoccupations of the rulers of the kingdoms of the time. It becomes clear that it is possible to discern a set of accepted practices which were generally followed by the kings from the time of Alexander to the approach of Rome. The republican states were less bound by such practices, and this applies above all to Rome and Carthage. By concentrating on diplomatic institutions and processes, therefore, it is possible to gain a new insight into the relations between the kingdoms.
This study investigates the making and duration of peace treaties, the purpose of so-called 'marriage alliances', the absence of summit meetings, and looks in detail at the relations between states from a diplomatic point of view, rather than only in terms of the wars they fought. The system which had emerged as a result of the personal relationships between Alexander's successors, continued in operation for at least two centuries. The intervention of Rome brought in a new great power which had no similar tradition, and the Hellenistic system crumbled therefore under Roman pressure.

This study of diplomacy in the Hellenistic period, a subject long neglected, describes the major institutions, particularly in the practices of concluding peace at the end of the many wars of that time. These practices are traced to their origin among the personal relationships between the warriors who succeeded Alexander the Great and who carved up his empire. They are then examined in operation in various parts of the Hellenistic world - Syria, Greece, the West - and the progressive destruction of the system by Rome.

"Grainger marshals his considerable knowledge of the Hellenistic world to make a good case for the unique character of international affairs in the two centuries after the death of Alexander, showing in the process what we can gain by explaining the interactions among the Antigonids, Seleucids, Ptolemies, and Romans in terms of their diplomacy, not simply of their wars ... Students of Hellenistic history who already have a good grasp on the major players, events, and territories will benefit from Grainger's palpable erudition and range and may find fresh treatments of particular episodes." - Daniel Tober, Fordham University, USA, Bruyn Mawr Classical Review 2018 "He [Grainger]does offer valuable insight into international relations between the great powers of the Hellenistic world." - Carol J. King, Memorial University, Mouseion: Journal of the Classical Association of Canada