Chapter 3 - The Military Revolution
Strategic and Tactical Mobility
A tremendous increase in strategic mobility resulted from the ability of Iron Age armies to deploy larger and larger armies and to sustain them logistically in the field. Strategic mobility can be defined as the ability of a military force to project influence and power over a given geographical area. The greater the area over which a military force is able to conduct military operations and sustain them over time, the greater the degree of strategic mobility. The ability of Iron Age armies to project military power over great distances was not equaled again until the armies of the 19th century.
The strategic range of a typical Bronze Age army was approximately 350 miles by 150 miles. The armies of Sumer and Akkad conducted military operations ranging from the Upper Tigris Valley to the city of Ur, or a range of about 250 miles by 125 miles. The armies of Egypt in the period 3000 to 1400 B.C. could project force from the Nile Valley to Syria, or a distance of 600 miles by 200 miles. With the dawn of the Iron Age, however, these strategic ranges increased greatly.
The Egyptian army of 1300 B.C. had a strategic range of 1,250 miles by 200 miles or more than twice the range of the earlier period. Assyria conducted military operations from Assur to Susa to Thebes, an area comprising 1,250 miles by 300 miles. This was five times the range of the armies of Sumer. The armies of Persia, Alexander, and Rome (see Maps 3, 4, 5) attained strategic ranges typical of modern-day armies. The Persian army, for example, conducted operations from the Iaxartes and Indus rivers to Thrace, Cyrene, and Thebes, a strategic range of 2,500 miles by 1,000 miles. Alexander's armies ranged from the Hellespont to the Caspian Sea to the Persian Gulf, a range of 2,600 miles by 1,000 miles. The greatest strategic range was achieved by the legions of Rome, which controlled an area from Germany to Morocco and from Scotland to Armenia and Babylon, a strategic range of 3,000 miles by 1,500 miles. On average, the armies of the late Iron Age had a strategic range that was nine times greater than the range of armies of the Bronze Age. Even in modern times only a few of the armies of the world can match the strategic range of the armies of the Iron Age.
Strategic range was very much a function of the ability of Iron Age societies to place the resources of the entire state at the service of military operations. Range also increased as a function of logistics and staff organization that rationalized planning. The utilization of naval forces in support of ground operations far from home also increased range and flexibility. It is important to remember, however, that armies moved on foot. No army of the modern period equaled or exceeded the rates of movement of the ancient armies until the American Civil War, when the use of the railroad made faster, large-troop movements possible.
The increased mobility of Iron Age armies was also a function of the military road. Early imperial states had the advantage of regular travel over regular routes, a practice that packed down and widened dirt trails into usable, good-weather roads. Regular routes of travel also made the use of military maps a standard practice. Maps were an important military resource. During the period of tribal invasions in Europe after the fall of Rome, accurate mapmaking all but disappeared as a military art. Commanders of armies of the Middle Ages often spent weeks roaming around the countryside in search of the enemy simply because they lacked maps that accurately displayed road and trail nets. By the time of the Persian empire, states had begun to construct regular roads for military purposes.
The Persian empire was tied together by a system of royal roads that facilitated military control and communication with the provinces on the empire's rim. The roads made it possible for the king to move forces quickly to any point within the empire to suppress civil unrest or meet a threat from outside. These roads were unpaved, packed dirt-tracks wide enough to support the movement of the mobile Persian siege towers drawn by teams of oxen. A system of bridges over streams and other terrain obstacles, more than the road surface itself, greatly increased rates of movement. The most famous of these roads ran from Sardis on the Mediterranean to the Persian capital of Susa, a distance of 1,500 miles. A messenger could travel this distance in 15 days using a series of horse relay stations. Without the road the journey would have taken 3 months.
The most effective and amazing system of military roads was the Roman roads, which crisscrossed the empire. The first Roman military road was built during the Samnite Wars and ran from Rome to Capua, a distance of 132 miles. Terrain obstacles were either leveled or crossed by bridges. Marshlands were crossed by raised roads built in the fashion of aqueducts. Low spots in the rivers and streams were provided with paved, underwater fording points. As Rome established her hegemony over the Western world, she connected the entire empire with a network of military roads. The Romans built over 240,000 miles of roads, 40,000 of which were paved, permanent roadways, most of which still exist. To place this achievement in perspective, the U.S. Interstate Highway System consists of 44,000 miles of paved roads. The effect on the mobility of the Roman armies was amazing. On dry, unpaved roads a Roman legion (6,000 men) could move about 8 miles a day. In wet weather, movement was almost impossible at any speed. On paved roads, however, a legion could move 25-30 miles a day in all kinds of weather. The Roman military road network not only increased strategic range and mobility but revolutionized logistics and transport as well.