What lies behind the strength of the Imperial Roman Army has generated considerable debate in modern scholarship, with mainstream opinion concluding that the imperial military power of Rome was strongly influenced by its organization and discipline. However, Adrian Goldsworthy stressed that military organization should not be overdone, saying that it was flexibility that was ultimately the key to its success. The strength of the army is seen explicitly in its ability to maintain control over the provinces. However, in order to assess the reasons for its power, it is essential to take into account the importance of the army's organization, its border system and its strategy, as well as its training and discipline. . The organization of the army as a standing professional army was introduced under Augustus in response to the civil war which had dominated the Republic. The primary function of an army is to wage war abroad, but under the Principate it became increasingly concerned with internal security and border defense systems. This is reflected in its organization. The basic structure of the Army that developed under the First Principle involved the creation of permanent units and the expansion of service. Tacitus describes the army as a complex system composed of the garrison, provincial troops and navy. The garrison was stationed in and around Rome and initially consisted of 10,000 men, divided between the Praetorian Guard, urban cohorts and vigilantes. The Praetorian Guard were the "elite" of the army, acting as the emperor's bodyguards, but they were also responsible for overseeing security and maintaining the peace. The guards characterize one of the central changes made by Augustus alo...... middle of article ......Oxford.Isaac, Benjamin (1988), 'The meaning of the terms Limes and Limitanei', Journal of Roman Studies 78, 125-147.Le Bohec, Y. (2000), The Imperial Roman Army, London.Luttwak, Edward (1976) The Grand Strategy of the Roman Empire: from the first century to the third century AD.- C., Baltimore and London. Roth, Jonathan (1994), "The Size and Organization of the Imperial Roman Legion", Historia Zeitschrift fÜr Alte Geschichte 43, 346-362. Roth, Jonathan (1999), The logistics of the Roman army at war (264 BC – AD). 235), Brill.Smith, R. E (1972), “The military reforms of Septimius Severus”, Historia Zeitschrift fÜr Alte Geschichte 21, 481-500. “Tacitus: Agricola”, http://www.sacred-texts. com/cla/tac/ag01020.htm (accessed 03.28.12).Thomas, C. (2004), “Claudius and the reforms of the Roman imperial army”, Historia Zeitschrift fÜr Alte Geschichte 53, 424-452.