In the year 1300 BC, there was a mighty clash as armies from two of the world’s largest empires met in battle. The Hittites swept down from the North while the Egyptians flew up from the South. By chance or design, they met about equal distance from each of their capitals at the town of Qadesh. But the town wasn’t close, the armies each had to travel 600 kilometres.
As the armies were on the march, they had to be supplied rather than forage. In those times, armies were quite simple; men and horses. The total energy cost for this battle can be then simply summed by knowing the biological costs of each of these.
A marching human male needs 15 000 000 joules each day.
A walking horse pulling a chariot needs 100 000 000 joules each day.
The Hittite’s Energy Cost
The Hittites journeyed forth with 40 000 men and 3 700 horses.
Assuming the Hittites journeyed non-stop at a rate of 20 kilometres a day then they’d need 60 days to travel from their capital to the battlefield and return. Hence, assuming they had wise, planners in their army, they’d need the following amount of energy delivered to them.
Men = 40 000 men * 15 000 000 joules each day * 60 days = 36 000 000 000 000 = 3.6e+13 joules
Horses = 3700 horses * 100 000 000 joules each day * 60 days = 22 200 000 000 000 = 2.2e+13 joules
In total, the Hittites needed 5.8e+13 joules for this campaign.
The Egyptian’s Energy Cost
The Egyptians set out with 4 corps of 5 000 men each. Of this, 4 000 were walking infantry and 1000 were in 2-man chariots pulled by two horses. Again assuming that their quarter masters were capable, they’d need the following amount of energy ready for them.
Men = 16 000 men * 15 000 000 joules each day * 60 days = 14 400 000 000 000 = 1.4e+13 joules
Horses = 2000 horses * 100 000 000 joules each day * 60 days = 12 000 000 000 000 = 1.2e+13 joules
In total, the Egyptians needed 2.6e+13 joules for this campaign.
Total
To sum up, humans used a total of 2.6e+13 joules or 26 terajoules (TJ). This amount of energy is about the same amount of energy needed to launch the space shuttle into orbit.
[1] Qadesh.