The Ptolemaic Dynasty ruled Egypt and much of the eastern Mediterranean basin for nearly 300 years. As a Macedonian dynasty, they derived much of their legitimacy from military activity. As an Egyptian dynasty, they derived much of their real wealth and power from maintaining a secure hold on their new homeland. As lords of a far-flung empire, they maintained much of their authority through garrisons and the threat of military action. To achieve this they devoted much of their activity to the development and maintenance of a large army and navy. This work focuses on the period of the first four Ptolemies, from the acquisition of Egypt after the death of Alexander the Great to the great battle of Raphia more than a century later. It offers a study of the Ptolemaic army as an institution, and of its military operations, both reconstructed through a wide range of ancient sources, from histories to documentary papyri and inscriptions to archaeological finds. It examines the reasons for Ptolemaic successes and failures, the causes and nature of military change and reform, and the particular details of the Ptolemaic army's soldier classes, unit organization, equipment, tactics, and the Ptolemaic state's strategy to compile a military history of the golden age of one of the classical world's significant forces.