The main reason of the Rome's expansion was its powerful army. All citizens between the ages of 17 and 60 had the duty to serve in the army.
Soldiers in the army were assigned to a legion, made up of 5.500 men.
During military campaigns, soldiers stayed in camps.
Each legion had its name and number and the total number of legions was between 30 and 50, not being all simultaneously.
Besides, roads were the other vital feature for the development of the Roman empire. The roads made possible for Romans to move armies, trade goods and communicate from one point of the vast empire to another one.
The soldiers built the roads under the instructions of experts in land and engineers, following a building technique which made them the first paved roads in the world.
As a consequence, the roads were, as well, the best means for expanding the Roman culture.
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