Economics of the Roman army

The economics of the Roman army concerns the costs of the Roman military establishment and the tax burden on the empire's inhabitants to support it.

The military burden

The size and growth of the Roman army of the Principate may be summarised as follows:

NOTE: Figures are based on official (not actual) unit strengths and exclude Roman navy effectives and barbarian "foederati".

In addition, the Roman navy contained probably 30-40,000 marines, sailors and oarsmen, of which 15-20,000 in the Mediterranean fleets at Misenum and Ravenna (contrary to popular belief, Roman warships of this period were not rowed by the forced labour of convicts or slaves, but by volunteer professional oarsmen) [Keppie (1996) 383] and perhaps the same again in the "classis Britannica" (English Channel fleet) and the fluvial flotillas on the Rhine and Danube.

Furthermore, substantial numbers of irregular barbarian troops ("foederati") were in the paid service of the empire during the whole period: we have no idea how many, but we know there were at least 5,500 in Britain alone about 175 (surrendered Sarmatian cavalry posted there by Marcus Aurelius). If we multiply this figure by 10 to represent other frontier provinces, it is possible that there may have been 50-60,000 such irregulars at any given time.

At its peak under emperor Septimius Severus (r. 197-211), therefore, the standing Roman military establishment may have comprised over half a million effectives.

This was a very significant burden on the Roman economy, which was pre-industrial: at least 80% of its inhabitants worked in agriculture. [Mattingly (2006) 356] Virtually all the taxes and rents raised by the imperial government were spent on the military: about 80% of the imperial budget in c. 150. [R. Duncan-Jones "Money and Government in the Roman empire" (1994) 45] This military spending constituted, on one estimate, about 2.5% of the empire's GDP, [Cf. article by R.W. Goldsmith in "Journal of the Int'l Assoc. for Research in Income and Wealth" Series 30 (1984) 263-88] which seems a tolerable burden if compared to the USA, today's global superpower, which spent 3.8% of its GDP on defence in 2006 (18% of the federal budget). [The Economist "Pocket World in Figures" (2007)] But the comparison is misleading. Due to modern technology, a modern economy is far more productive per capita than the Roman economy: on one estimate, the average American in 1998 was at least 73 times more economically productive, in comparable terms (i.e. in international dollars), than a Roman in the 1st century AD. [Derived from historical GDP estimates in A. Madison "The World Economy: a Millennial Perspective" (2001)] Therefore, taxes (and compulsory services) to support the Roman military would have taken a much greater share of surplus per capita production i.e. surplus to the subsistence needs of producers. For the average peasant, the taxes and services he was obliged to provide to the military would have represented a significant share of his disposable surplus.

There is also a great disparity between the costs of the 4th century army and its 2nd century counterpart. The much lower remuneration for 4th century soldiers is reflected in total army costs. Duncan-Jones estimates the total annual cost of the military in c150 AD at c670 million "sesterces". [Duncan-Jones (1994) 45] That translates into 6.7 million "aurei" or 168,000 pounds of gold. This compares with Elton's estimate of c47,000 lbs of gold for a 4th c. military establishment of 450,000. Even if the establishment was the 600,000 estimated by A. H. M. Jones, the cost would still be only about a third that for the 2nd c. army. [Elton (1996) 124] Such a disparity is difficult to explain. Either the imperial government was collecting far less tax than in the 2nd century (an unlikely possibility, given the numerous complaints about the weight of the tax burden). Or it was spending much more on other sectors. These may still have been "defence-related": e.g. fortifications, irregular "foederati" forces, or payments to barbarian chiefs to buy peace and allegiance. The latter had a long history: such payments are recorded in Julio-Claudian times.

Notes