That word, "colonization" comes from Latin colere, "to cultivate" > colonus: "farmer, settler" > colonia "landed estate" (under the Roman empire became territories seized in other countries: colonies).

Attacks on the Common People

            Christianization of the empire did not bring about the liberation of slaves or oppressed colonies. Instead it provided a religious rationale for domination: that the social hierarchy was divinely ordained. Romans 13:2 sided with the powers-that-be over the oppressed, whose duty was to obey. Even though some early bishops had been slaves, the bishops now sat in state-sanctioned pomp and privilege. They upheld the class hierarchy of the Roman world, an imperialist slave society. Some were slaveholders themselves, [Lane Fox, 296] as were their leading congregants. Thus the new world order operated very much like the old one, but under a new religious rationale.

           Paul’s injunction that servants obey their masters was repeated in Timothy 6:1: “Let as many slaves as are under the yoke count their own masters worthy of all honor, so that the name of God and his doctrine not be blasphemed.” (Here men’s customary and endemic rape of slaves is conveniently disregarded.) In Paul’s Letter to Philemon, he returns a fugitive slave back to his master, advising that he be treated leniently. Church councils of the 500s and 600s cited this letter to justify refusing asylum to escaped slaves. [Dockès, 146] (It later got a heavy workout in 19^th century America.) In the 370s, Basil of Caesarea had ordered monasteries to return runaway slaves. [Bradley, 147-8]

           The legal status of slaves remained much the same. Constantine banned the practice of face-branding, although he left the door open to mutilation and murder. His law of 319 reassured the slaveholder who beat or whipped or chained up his human chattel that “he should not stand in fear of any criminal accusation if the slave dies”—as long as he had not used weapons to murder the person. [Phillips, 27] Contemporary sources show little change of heart among Christian slaveholders, least of all the high clergy. [Bradley, 147] The Council of Elvira penalized nuns who married far more severely than a woman who killed her slave. [Hefèle, I.1, 225, 229]

           Some early female saints repudiated the slaveholding system they were born into, thus upholding  the earliest principles of their religion. Macrina included her freed slaves in her house convent, “making them her sisters and equals rather than her slaves and underlings.” Olympias of Constantinople did the same. [McNamara, 78] Others had difficulty detaching from the privileged mentality that regarded humans as property. Around 400, the devout Roman heiress Melania and her husband Pinian resolved to follow Yeshua's instruction to “Sell all you have, and give to the poor.” However, the poorest of all—those who were themselves regarded as property—were not to be beneficiaries of this largesse. Most of them were slated for sale.

Melania's slaves rebelled when word spread of the plan. They were terrified by the probability of being sold away from their loved ones, and they tried to stay together by going to Pinian's brother. (For trying to aid them, he was accused of trying to enrich himself.) With help from the emperor's family, Melania and Pinian won a decree that the state would sell their chattel and give them the money. The slaves were duly sold to the highest bidders, so that the pious couple would have the more to distribute as alms. [Pagels, 87-8. Melania's priestly biographer claims that she freed 8,000 out of 24,000. Phillips (1985: 35) thinks this number exagerrated.]

Judgment Day: Christ enthroned amidst kings and lords, while cavalry cuts down suffering humanity below:
“a sharp sword to strike down the nations” which “he will rule with a rod of iron.” —Book of Revelations.

           Some church fathers blamed slaves for their misfortune. Augustine believed that slaves—who were originally captives—had brought their suffering on themselves: “such a condition of servitude could only have arisen as a result of sin, since whenever a just war is waged the opposing side must be in the wrong, and every victory, even when won by wicked men, is a divine judgment to humble the conquered and to reform or punish their sin.” Augustine made several facile assumptions: that Rome’s imperial wars were just, and that the captives they took were sinful, more sinful than the Romans who enslaved them. “It is clear, then, that sin is the primary cause of servitude... Nor does this befall a man, save by the decree of God, who is never unjust...” [City of God, XIX, 15 (2008: 223)] Isidore of Seville agreed, opining that the system of masters and slaves was divinely willed. Pope Gregory “the Great” wrote on similar lines, and himself bought captive Britons in the Roman slave market. [Dockès, 146]

          The accommodation of Christianity to Roman social hierarchy that began with Paul continued to deepen. By the 3rd century, hegemonic rank in the institutional church had outstripped the Nazarene’s teachings of love and humility. As Karen Torjesen explains, Tertullian treated the church as a political body, with bishops as its monarchs. He redefined ministry in legalistic terms, as a privilege linked to class, but even more to sex. Thus women lacked the rights of clergy: jus docendi (the right to teach); ius offrendi (the right to make ritual offerings); and ius delecta donandi (to restore sinners after penitence). Tertullian complained that local churches failed to uphold differences of rank and to observe the proper distance between social orders. He saw such Christians as heretics, “without gravity, without authority and without discipline.” [Torjesen, 160-4]

           Many Christians disagreed with the ecclasiatics’ claim that state power was divinely ordained, not forgetting that they themselves had been persecuted by that power. But the authoritarian wing managed to dominate the Christian movement through its privileged relationship with the state. The bishops used state power to reverse the policy of religious toleration for which their predecessors had given their lives, and persecuted other Christians as heretics.

           To rebel against the church and its patriarchal canons, said the priestly hierarchy, was to rebel against god. These claims represent the most extremist trend in the Christian movement. But it was this authoritarian model that prevailed, laying the foundations of the oppressive partnership of church and state that would rule the late empire, and then medieval Europe.

           That’s the doctrinal ideology around the class system. But to really understand the brutality of the class system in the Roman empire, we need to look at the bare facts of colonization. As the empire expanded around 200 bce, small farmers were drafted to serve in its armies, and for increasingly long periods. The legions systematically sold war captives—Syrians, Gauls, Britons, North Africans, Arabians, and Danubian peoples—into slavery on a vast scale. The empire ran as a slavery economy for centuries. And as the legions enslaved multitudes as they conquered lands from Portugal to Persia, and from Mauretania to the Rhineland, countless conquered “provincials” joined their ranks. So far had empire stirred the pot of nationalities, that Sarmatians were stationed in Britain, and Iberians in the Adriatic. They brought their religions with them, so that temples rose to Kybele in Germany and Gaul, and monuments to the Celtic horse goddess Epona all over Europe, as far as Greece. Syrians enslaved in Sicily even launched insurrections under the banner of Atargatis.

It became difficult for all those militarized Italian peasants to work or even hold on to their land. They were subjected to the rapacity of imperial agents, tax-collectors, and press-gangs. A bad harvest meant famine and debt. Many people were forced to sell their farms to the wealthy elite, who turned them into huge latifundia. These plantations were worked by enslaved people, often side by side with impoverished peasants (now reduced to sharecropper tenants). They produced grain, oil, wine, cheese, and beef not for subsistence, but as cash crops for export. They lived and worked under dire conditions, sometimes chained in the notorious ergastula, roofed pits in the earth. Slavery persisted through and beyond the fall of the Roman empire.

Thus, certain powerful men became extremely rich, and the race of slaves multiplied throughout the country, while the Italian people dwindled in numbers and strength, being oppressed by penury, taxes, and military service. —Appian, Roman History: The Civil Wars LCL 4: 16-1. [He describes the extent of their expropriation here: heehttps://www.26reads.com/library/91079-the-roman-history/2/1/2 ]

 As wealth became more and more concentrated, rich landholders swallowed up the lands of most smallholders, including veterans who had obtained land from military service. Where did these people go? Most stayed as laborers on their own land, now as sharecroppers forced to pay a large tribute of their produce to the rich estate-holders. They were coloni: a term that originated with the conquest and settlement of foreign countries, but came to be applied to the increasingly oppressed farmers. [Mackay, 298] They became bound to the land as serfs known as coloni.

This process began with edicts of Diocletian circa 300 CE, which tied coloni to the land in order to increase state revenues. He also wanted to ensure a grain supply to the military, which was increasingly hard-pressed in a time of crisis. So a pagan emperor began this process of enserfment. But it got much worse under the Christian emperors. The laws of Constantine and his successors insist on the unfree status of coloni. (Note: this word is rendered as “serfs” in the translation I’m using, which is confusing because in Latin servi means “slaves,” a distinct and even more oppressed class. I’ll use coloni, but keep the reading “serfs” in direct quotes.) Let’s look at the hard reality:

The coloni were drawn from impoverished small free farmers, partially emancipated slaves, and barbarians sent to work as agricultural labourers among landed proprietors. For the lands that they rented, they paid in money, produce, or service. Some may have become coloni in order to gain protection from the proprietor against the state tax collector or against invaders and aggressive neighbours. Although technically freemen, the coloni were bound to the soil by debts that were heritable and by laws limiting their freedom of movement. By AD 332 landlords were permitted to chain coloni suspected of planning to leave. [www.britannica.com/topic/colonus-ancient-tenant-farmer ]

Constantine’s law defines the bonded status of coloni, who are attached to a specific estate and cannot leave. [Corpus Iuris Civilis XI. 47. 2] This class of coloni were called adscripticii glebae, “registered to the soil,” a category that soon swallowed up free tenant farmers (and would  persist in feudal Europe for many centuries to come). Many of these peasants fled. Valentinian and Valens refer to “vagrant slaves from deserted lands,” in demanding that landlords must still pay grain tribute to the state (a demand the emperors kept repeating). [XI. 47. 3] They decree that provincial governors “shall compel all fugitive serfs” (and any other tenants) “to return to the land where they are registered, and where they are born and reared.” Coloni cannot be sold, but go with the land they are bound to. [XI. 47. 6-7]

The emperors refer, often and repeatedly, to “fugitive serfs” who hide on other estates, concealing  “their servile condition,” and pretending to be free laborers. [Corpus Iuris Civilis XI. 47. 8; 15; 23.2; 63] Emperors Arcadius and Honorius reiterate the claim that serfs have no rights, and must be “restored to their owner, or to the land to which they were attached.” (These laws indicate that a lot of people were escaping.) They impose big fines for landowners who harbor fugitives, a penalty that is extended to other provinces. [Corpus Iuris Civilis XI. 47. 51-53] They punished the captured coloni by chaining, flogging, or beating them.

Eventually, imperial law collapses class categories into a single servitude: “slaves, tributary serfs, or tenants shall remain with their masters…” And again, “We decree that, so far as the origin of tenants and serfs is concerned, they shall be considered as of the same condition…” [Corpus Iuris Civilis XI. 47. 11-12] Real differences of status still existed in practice, but the trend was to expand the numbers under subjugation and severely curb their liberty: “We declare that serfs are so absolutely attached to the glebe [plot of farmland, literally “soil”] that they should not be removed therefrom for a single instant of time.” For that reason, they were barred the army, which would have offered men, at least, a route of escape. [Corpus Iuris Civilis XI 47.16; 19]

As in American slavery, the Roman empire settled on matrilineal descent as the determinant of class status. This was a much-discussed topic: what if a female colona has a child by a slave, or a freeman, or any combination of sex and class status? [Corpus Iuris Civilis XI 47. 16; 21; 24; 53.2] (Note that women are only mentioned in the context of motherhood, purely to establish class status.) The emperors were keen to lock people into bondage; even if a colonus has lived free for 40 years, away from the glebe of his serf, he must return at his father’s death. Because, says Justinian: “it seems to Us to be very harsh that the rights of the master should be prejudiced by the absence of his serfs.” So,  “The rights of the owner shall therefore remain unimpaired…” [Corpus Iuris Civilis XI 47. 22] Arcadius and Honorius agreed: “it would be extremely unjust” for landowners to incur losses from coloni who run away, no matter how long they stay away, or whatever negotiations they attempt:

…but he shall always remain a serf, and be attached to the glebe; and if he should lie concealed, or attempt to withdraw from the soil, he shall, like a fugitive slave, be understood to have stolen himself by long-continued treachery, and shall remain in this class, together with all his offspring… and shall be liable to the payment of quit-rent [a fee in lieu of labor-service], from which he cannot be released by any act of generosity whatsoever. [Corpus Iuris Civilis XI. 47. 23]

Coloni must never be permitted to rise in station or to live elsewhere. These provisions are repeated  for other imperial provinces: “We now decree that no serf of Palestine shall have the right to wander about, and boast that he is free, but shall, as in other provinces, be subject to the proprietor of the land, so that he cannot depart therefrom without being liable to punishment…” [Corpus Iuris Civilis XI 50.1] The same went for Thrace (Bulgaria), whose peasants were no longer free, but subject to overlords:

…even though they may appear to be freeborn, they shall still be considered to be attached to the land where they originated; nor shall they have the power to go wherever they choose, or to change their residence, but the owners of the land shall exercise over them the rights and care of patrons and the authority of masters. [Corpus Iuris Civilis XI 47. 51]

           These excerpts from the laws of the Christian emperors show no trend toward kind treatment or  liberalization, but intead a ruthless extension of class dominion over ever-increasing numbers of people. The common people—now coloni—were literally being colonized, to a degree unprecedented in Roman history. It was in this context that the bishops were preaching “servants obey your masters,” and that Augustine was blaming the suffering of people in servitude on their own sinfulness—not the rapacious greed of those who held them in bondage. This evil precedent cast a long historical shadow.