Polybius was a Greek historian, who lived from around 200 BC to around 118 BC. He wrote a history of the rise of the Roman Empire while being held as a political prisoner in Italy, where he had been deported after Rome's victory over Perseus, the last king of Macedon, in 168 BC.
Polybius' 40-volume work, The Histories, written in the second century BC, of which only five full volumes still exist, touches on a number of topics such as the role of fate and divine influence on the fortunes of nations and the critical analysis of other historians. He also elaborated a theory of anacyclosis, which proposed that forms of government are cyclical and follow a fixed pattern of moving from kingship by a just ruler, to hereditary monarchy which leads to tyranny under a corrupt monarch, which leads to aristocracy as the bureaucrats revolt, which degenerates to oligarchy, which is then supplanted by a democratic revolution, which then degenerates to mob rule. The resulting chaos is resolved when a single charismatic leader rises to power, thus starting the cycle over again at kingship. Polybius proposed that the mixed constitution of Rome broke this cycle by combining aspects of Monarchy (the Consuls), Aristocracy (the Senate) and Democracy simultaneously. Polybius' writings on the value of a mixed constitution, although not influential in their day, became popular once again upon their introduction to the West in the 15th century.
Polybius is also credited as the creator of the Polybius checkerboard, in which the letters of an alphabet are placed in the squares of a grid. Messages can then be transmitted by indicating the row and column of individual letters using a number of simple techniques, such as flashing lights, drum beats, or patterns of knots on a cord. This technique is easier to learn than Morse code, but is less efficient.