Select excerpts from Karen Metz's "From Sumer to Rome".
In the 8th century B.C., when the entire Assyrian army included 150,000-200,000 men, a combat field army of 50,000 men would be equal to 5 modern American heavy divisions, or 8 Soviet field divisions.
When arrayed for battle, a field army occupied an area of 2,500 yards (almost 1.5 miles) across and 100 yards deep. After the fall of Rome, it was not until Napoloen's re-institution of conscription that armies of such a size would be mustered.
The Assyrians were the first to invent large cavalry squadrons.
A special logistics branch, the Musarkisus, was created to keep the army supplied with horses. It was able to obtain 3,000 horses a month for military use. Once again, it was not until Napoleon that such large amounts of horses would be systematically procdured for the army.
In a climate such as the Middle East, a soldier would need 3,402 calories a day and 70 grams of protein to sustain him, in addition to 9 quarts of water.
A ration of 3 pounds of wheat daily (or 150,000 pounds daily for a field army) would only provide 2,205 calories daily, insufficient for the needs of a soldier.
The "strategic mobility" of the Assyrian army, or their ability to project their military force over a given area, was 375,000 square miles. After Rome fell, no army exceeded this area until the American Civil War, when the use of railroads made troop movements easier.
In terms of efficiency of organization, no military staff (i.e. administrators, logistic officers and engineers) would reach the proficiency of the Assyrian or Roman military staffs until the German general staff of the 1870's.
The prototype of a modern soldier's equipment (helmet, body armor, boots [a particular Assyrian innovation], and backpack) was invented by ancient armies and disappeared for almost 1,000 years after the fall of the Roman Empire.
The killing power of an ancient composite bow (i.e. the accuracy, force, distance, and speed of deployment) was not matched until the introduction of the Prussian needle gun in 1871.
According to modern tests, the body armor, helmet, and shield of the Assyrians would have provided excellent protection against firearms until Napoleon. If the dispersion of field formations, inaccuracy of early firearms, and rates of fire are considered, the Assyrian soldier would have been safer on a battlefield in the 18th century than on an Ancient Near Eastern one.
Source: Richard A. Gabriel and Karen S. Metz. "From Sumer to Rome: The Military Capabilities of Ancient Armies." New York: Greenwood Press, 1991.