Aeneas Tacticus
Aeneas Tacticus was one of the earliest Greek writers on the art of war and is credited as the first author to provide a complete guide to securing military communications. Polybius described his design for a hydraulic semaphore system. His only surviving work, How to Survive Under Siege, covers how to defend a fortified city that is under siege. The work gives instruction to not just military commanders but also the citizens of the city under attack, providing secure communication, internal security, and how to keep morale high. This work is what credits him with having the oldest known book on defense warfare in Greek literature. He also provides a lot of insight into the politics within the classical polis.
According to Aelianus Tacticus and Polybius, he wrote a number of treatises on the subject. The only extant one, How to Survive under Siege, deals with the best methods of defending a fortified city. Aeneas describes how one should choose trustworthy guards to maintain the secure communications to detect internal conspiracies, as well as simpler tactics like securing the surrounding walls and gates. An epitome of the whole was made by Cineas, minister of Pyrrhus, king of Epirus. The work is chiefly valuable as containing a large number of historical illustrations.
Aeneas was considered by Isaac Casaubon to have been a contemporary of Xenophon and identical with the Arcadian general Aeneas of Stymphalus, whom Xenophon mentions as fighting at the Battle of Mantinea (362 BC). Most modern historians agree that there's little that can be confirmed about Aeneas's life, and details about him are suggested from themes reflected the surviving treatise. Through his writing you can see the correlation between defensive challenges and political instability within the Greek city-states during the 4th century BC. This shows he had experiences in domestic security or civic defense.He also is dated to have one of the first known references to a hydraulic telegraph, with his own design innovating the signaling device to transmit prearranged messages across far distances. The machine uses two matching containers filled with water that have marked rods. The user would open the plugs in each at the same time and would then close them when a signal appeared, likely a torch. This would cause the water level to fall to mark corresponding to the intended message. Polybius did provide a more technical description later on but Aeneas's account still dating first.
Aeneas's treatise sustained its influence with writers on military theory after his time. Aelianus Tacticus and Polybius both refer to him as a pioneer on communication and military tactics, showing the value others had on his observations. How to Survive Under Siege is viewed as an important document for the understanding of the ins and outs of internal security and urban defense in Classical Greece by modern scholarship. Recent studies emphasize the treatise's blend of insight into civic organization and practical instruction which can make it a strong source for historians of both warfare and political life.