When Rome took control of a foreign city, through a military or diplomatic conquest, it was incorporated into the Roman state becoming a Municipality, otherwise, when Rome founded a new settlement from nothing, the new city was a Colony. In the Roman world there were no other options, all the cities under the control of Rome were Colonies or Municipalities, while the foreign cities, allied with Rome and linked to Rome by an alliance were Foedus, and called Soci or Federate di Roma.
I Foedus , which we can translate as fiefdoms, were the ancestors of the medieval fiefdoms , and constituted non-Roman settlements, linked to Rome by treaties, called precisely Foedus, which sanctioned an alliance between Rome and that settlement or even an entire people.
The Feodus Cassianum
One of the most famous and important Foedus in Roman history is the Foedus Cassianum , a treaty stipulated around 493 BC between Romans and Latins.
This Foedus was stipulated at the dawn of the republic, and was one of the effects of the transition from monarchy to republic.
With the deposition of the last king of Rome, and the establishment of the Republic, Rome found itself facing a period of internal crisis, which on the one hand led to the exclusion of the plebs from public office, in particular, Tito Livio , in the work Ad Urbe Conditia Libri , tells us that with the passage to the republic, the plebs were excluded from the consulate, that is to say from the government of the cities, from the religious colleges and other high magistracies, which instead, in the republican age did not happen and de facto, a plebeian or even a foreigner could not only assume the government of a city, but even become King, as had happened with several kings, in particular with the last three kings of the Roman tradition, Tarquinio Prisco, Servio Tullio and the last king of Rome, Tarquinio the Superb , they were in fact of Etruscan origin, arrived in Rome as foreigners and thanks to their wealth and political alliances, they had managed to become sovereigns of the city.
With the end of the monarchy, Rome wanted to prevent other foreigners from taking control of the city, and the Roman aristocracy, coinciding with the patrician people, reserved the main institutional positions for themselves.
This very tense internal political climate led many Latin cities, under the control of Rome or allied with Rome in Lazio, to unite in an anti-Roman key, in what would have been the Latin League, protagonist of the famous battle of Lake Regillo, in which Rome succeeded in overcoming its rivals and imposing the Foedus Cassianum, named after the consul Spurius Cassio Vecellino.
The Foedus cassianum provided that in the event of battle, the various allied cities of Rome would take command of the Roman army, and the citizens of the Foedus allies of Rome could marry and trade freely with Roman citizens, as holders of the Ius commercii and the ius connubi, precisely the right of trade and marriage.
The Roman Feodus
Citizens of the foedus, however, could not become Roman citizens, and their social status fell under the ius emigrandi, they were therefore seen by Rome as foreigners, with more rights than other foreigners, but still foreigners.
Except for the part of the treaty that concerned the military alliance, the ius commercii, the ius connubi and the ius emigrandi , will be recurring elements in the various and numerous subsequent alliance treaties, defining those allied cities, as socii or as federates of Rome.
The cities linked to Rome as foedus, are foreign cities, even if strongly influenced by Roman culture, otherwise the Municipia were Roman cities, even if not founded by Rome.
There are countless episodes in which Rome managed to increase its influence on the allied cities, causing their status to pass from Foedus to Municipia.
The Roman Municipia
When a city became a Municipia, its citizens, especially the aristocracy, have rights and duties towards Rome.
The purpose of the municipia was to facilitate the Romanization of the territories, especially the Latin ones, following the subjugation of the local communities, which could take place in two ways, either with the military conquest, or with the diplomatic conquest, passing precisely through the foedus.
Although controlled by Rome, and the aristocracy of the municipia acquired Roman citizenship by right, with all that ensued, while the plebs obtained the status of Latin citizenship, the municipia maintained their own autonomy, and very often maintained a form of city organization, separate and distinct from the Roman organization.
Things begin to change with the advent of the Augustan principality and the formation of the empire, especially from Tiberius forward, marking a growing policy of Romanization of the empire that would end with the emperor Caracalla, promoter of the Costitutio Antoniniana in 212 d.c. which extended Roman citizenship to all peoples of the empire.
The municipia were initially only the cities subdued by Rome in the Lazio area, but with the expansion of the empire, the municipia tool was used everywhere in the Italian peninsula first and then in the Mediterranean basin.
In the first and second centuries after Christ, most of the cities subdued by Rome enjoyed the status of municipia and integrated Roman laws and traditions, with local laws and traditions, in a hierarchical structure so that local laws were fine as long as they were not in conflict with Roman law, and when there was a conflict, Roman law prevailed over local laws. Cities that, on the other hand, like Carthage, they had not accepted the transition willingly, they had been razed to the ground and rebuilt as a colony, and this brings us to the third and final piece of the organizational structure of Roman cities, namely the colonies.
The Roman colonies
If the Foedus were allied foreign cities, and the Municipia were conquered cities, the Colonies were real new settlements, founded by Roman citizens by the will of Rome itself.
The inhabitants of the colonies were Roman in all respects, or at most Latin, the communities lived according to the organizational rules of Rome, followed the Roman law and traditions, without too much foreign interference.
In the Roman world, at least until 212, all the cities of the empire fell into one of these categories, the old cities existing before the Roman conquest were Municipia, the newly formed cities were colonies, and in both cases this was true regardless of the size of the city, settlement or number of inhabitants.
Commercial settlements
There is, however, a type of settlement, which is neither a foedus, nor a municipality, nor a colony, and these are commercial settlements.
These settlements do not fall under the law of Roman cities because de facto they were not cities, nor villages, and most often consisted of a few warehouses along the road, rivers and coast. Often they also housed a tavern and a brothel and were manned by armed men, but they had nothing else, they were not cities, they were not villages, they were simple stations of passage, totally dependent on the transit of traders, without which those settlements could not survive because without water and food sources.