05-20-2005, 06:35 PM
This subject has been discussed before, and I would like to refer interested parties to this conversation: http://netsword.com/ubb/Forum4/HTML/000134.html and http://netsword.com/ubb/Forum4/HTML/000135.html . The context is medieval rather than ancient, but the mathematics are the same. Men and horses need food and water, and in the late 19th and 20th centuries army quartermasters worked out how much of each was needed per man and horse. The basic biology of men and horses hasn't changed much since Xerxes' time, so while 20th century figures might be off by a small fraction, they are a sound basis for calculation.
When considering the size of armies, it is worth remembering that the combined total of both sides in the largest battle of the Napoleonic Wars was about 500,000 (Leipzig, 1813). This is also about the size of the largest single force mustered in the Napoleonic Wars, the invading force that Napoleon launched into Russia in 1812. The Grand Armee was divided into three major groups marching along different axes, but even so, starvation played a major role in Napoleon's failure.
I see a "3:1" ratio has been brought up as a force needed to expect success. This is not the size of the total forces. It is a measure of the superior odds needed to attack successfully at a single point. Even then, it assumes the forces are comparable (in troop quality, gear, and without major advantage in terrain or fortification). "Three to One" has nothing to do with the overall size of armies. If you look at more modern warfare, for which reasonably good numbers are available, you will find few (if any!) major battles in either the Napoleonic Wars, the American Civil War, or the World Wars for which the attacking army was 300% stronger than the defense. What you more typically find is that the victors were three times as strong at the critical time and place, broke through the defense, and the rest of the line crumbled.
A simple calculation, by the way, on the length of Xerxes' army. Five million people, say each man or woman takes up 2 feet of a marching column, say they are 10 abreast - 5,000,000 x 2 /10 = 1,000,000 feet long. In miles (divide by 5280), this column is 189 miles long. This assumes perfect spacing and coordination of the march, no horses, no carts/wagons for baggage. For most armies, 20 miles a day was a good march - this column would take 10 days to march past a single point / bridge.
The numbers of Herodotus don't work. Even one-tenth the numbers strain credulity.
When considering the size of armies, it is worth remembering that the combined total of both sides in the largest battle of the Napoleonic Wars was about 500,000 (Leipzig, 1813). This is also about the size of the largest single force mustered in the Napoleonic Wars, the invading force that Napoleon launched into Russia in 1812. The Grand Armee was divided into three major groups marching along different axes, but even so, starvation played a major role in Napoleon's failure.
I see a "3:1" ratio has been brought up as a force needed to expect success. This is not the size of the total forces. It is a measure of the superior odds needed to attack successfully at a single point. Even then, it assumes the forces are comparable (in troop quality, gear, and without major advantage in terrain or fortification). "Three to One" has nothing to do with the overall size of armies. If you look at more modern warfare, for which reasonably good numbers are available, you will find few (if any!) major battles in either the Napoleonic Wars, the American Civil War, or the World Wars for which the attacking army was 300% stronger than the defense. What you more typically find is that the victors were three times as strong at the critical time and place, broke through the defense, and the rest of the line crumbled.
A simple calculation, by the way, on the length of Xerxes' army. Five million people, say each man or woman takes up 2 feet of a marching column, say they are 10 abreast - 5,000,000 x 2 /10 = 1,000,000 feet long. In miles (divide by 5280), this column is 189 miles long. This assumes perfect spacing and coordination of the march, no horses, no carts/wagons for baggage. For most armies, 20 miles a day was a good march - this column would take 10 days to march past a single point / bridge.
The numbers of Herodotus don't work. Even one-tenth the numbers strain credulity.
Felix Wang
