Chapter 3 - The Military Revolution
Size of Armies
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While the armies of the Bronze Age were quite large compared to those at the beginning of the period, they were minuscule by comparison to the armies that fought in the Iron Age. The Persians routinely deployed field armies that were ten times larger than anything seen in the Bronze Age. While the army of Sargon of Akkad in 2300 B.C. is estimated to have been as large as 5,400 men, an army of this size represented a supreme national effort and even then could be deployed in the field for only a short time. In any case, it remained the exception to the rule of much smaller Bronze Age armies.

Some examples of the size of Iron Age armies are instructive. The Egyptian army in the time of Ramses II (1300 B.C.) has been estimated at more than 100,000 men. This force was comprised largely of conscripts, most of whom garrisoned strong points throughout the empire and carried out public works projects. The actual field army was organized into divisions of 5,000 men that could be deployed individually or as a combined force of several divisions. The Battle of Kadesh in 1304 B.C. between the Hittites and the Egyptians is the first ancient battle for which we have accurate strength figures. In that battle the Egyptians mounted a four division force of 20,000 men against the Hittite army of 17,000.

The Assyrian army of the 8th century B.C. was comprised of at least 150-200 thousand men and was the largest standing military force that the Middle East had witnessed to this time. An Assyrian combat field army numbered approximately 50,000 men with various mixes of infantry, chariots, and cavalry. In modern times the size of an Assyrian field army was equal to five modern heavy American divisions or almost eight Soviet field divisions. When arrayed for battle the army took up an area of 2,500 yards across the front and 100 yards deep. The Assyrian army was also the first army to be entirely equipped with iron weapons.

Even the Assyrian army, as great as its size was, was easily dwarfed by the Persian armies that appeared 300 years later. Darius' army in the Scythian campaign numbered 200,000, and the force deployed by Xerxes against the Greeks comprised 300,000 men and 60,000 horsemen. General Percy-Sykes' analysis of Xerxes' army suggests that the total force, including support troops, numbered a million men! Even at the end of the empire the Persians could deploy very large forces. In 331 B.C., just before Alexander destroyed the Persian empire at the Battle of Arbela. Darius III fielded a force of 300,000 men, 40,000 cavalry, 250 chariots, and 50 elephants.

Philip of Macedon could field a combat army of 32,000 men organized in four divisions of 8,192 men each, and the army of Alexander sometimes exceeded 60,000 men. Roman military forces, which at the end of the empire totaled 350,000 men, could routinely field armies upward of 40,000. At the Battle of Cannae[note] the Roman force arrayed against Hannibal was 80,000 men strong. Of these, 70,000 were destroyed in a single day! The one exception to the ability of Iron Age states to deploy large armies was the armies of classical Greece. Being products of relatively small city-states, classical armies were unusually small even for the Bronze Age. Ahab, for example, at the Battle of Ai could field 30,000 men, while at the Battle of Marathon the Greeks were able to field only 10,000 men against the Persian force of 50,000. Thucydides recorded that at the beginning of the Peloponnesian wars in 431 B.C., Athens could field only 13,000 hoplites, 16,000 older garrison soldiers, 1,200 mounted men, and 1,600 archers. But even these small numbers represented a supreme military effort for Athens in time of crisis. Thucydides noted that after the military situation had stabilized a decade later, Athens could muster only 1,300 hoplites and 1,000 horsemen. It is little wonder, then, that battles of the classical Greek period usually involved no more than 20,000 combatants on both sides.

The growth in the size of armies in the Iron Age was almost exponential when compared to earlier armies. Sustained by larger populations, cheap and plentiful weapons, the need to govern larger land areas of imperial dimension, and the evolving ability to exercise command and control over larger military establishments, the armies of this period were bigger than anything the world had seen to this point. The armies of the Iron Age were truly modern armies in terms of their size. Following the fall of Rome in the 5th century A.D., few European states were able to muster such large military establishments until well into the 19th century. The large conscript armies of Napoleon were exceptions, and following his defeat European armies returned to the practice of retaining relatively small standing armies until well into the following century.

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