Army Supplies
A Roman legion was a vast body of men who all required food. A soldier's daily grain ration was the equivalent of 1.5 kg (ca. 3 lb 5 oz), which was generally supplemented with other foodstuff.
However, this meant that the total consumption of grain was around 7500 kg a day. Together with up to 500 kg of fodder for the animals this made a substantial amount of food.
In military bases, units were heavily involved in their own supply. Land was set aside for the use of the military to plant crops and graze their animals. These lands were referred to either as prata (meadow), or simply as territorium (territory).
Herds of cattle were also kept, watched over by soldiers called pecuarii (herdsmen). There are reports, particularly in the later empire of large numbers of limitanei (frontier guardsmen) who acted as soldier-farmers, charged with growing the crops for the troops.
Estimates of yield in Roman-style farming vary from 2000 kg to 500 kg per hectare land. These estimates result in land being required in the region between 7.5 km x 7.5 km and 3.5 km x 3.5 km to produce enough grain to feed the men. Add to this the necessity for additional land to grow grain and forage for the animals and one can only conclude that the military bases on the frontiers of the empire were far more than mere fortified headquarters, but large agricultural estates.
It also gives us an impression of the logistical difficulties of bringing up food when the armies were on campaign.
In some areas though grain could simply not be grown on the scale required and had to be imported.
Merchants would fulfil the function of shipping the grain from its point of origin to the army bases. But so too veterans and even some acting soldiers were involved in the trade.
Further food was brought in by hunting expeditions. Archaeologists have unearthed the remains of deer, foxes, even bears in the scrap heaps of military camps.
And yet an army was not supplied with food alone. Wine beer and olive oil had largely to be imported.
But so too, was there a constant need for other materials. Leather, iron and wood for repairs to equipment as well as for heating and cooking.
Clothing, too, would need to be replaced.
And for the maintenance of any army base, stores of building materials would be needed. A regular legionary fortress would be built of something akin to 15000 cubic metres of stone, alongside other materials.