The term “Black Robe Regiment” referred not to a literal regiment of soldiers that wore black robes into battle but rather to the influential clergymen who promoted American independence and supported the military struggle against Britain. By encouraging the Patriot cause, those ministers helped muster critical support among members of their congregation—support the British begrudgingly acknowledged as vital to maintaining the colonists' frustrating resistance to British attempts to restore Parliamentary rule. In its implicit comparison of symbolic support to a specific body of troops, the term “Black Robe Regiment” is somewhat similar to the “fifth column” identified by the Spanish general Emilio Mola. During that country’s Civil War in 1936, Mola boasted that he had four columns of soldiers marching upon Madrid and a “fifth column” of sympathizers already living in the city who would support the army once it arrived. The term “fifth column” has since come to refer generally to civilian supporters living within a populace, even though that group usually lacks formal organization. Likewise, the Black Robe Regiment was not an actual detachment in the Continental Army but rather a British epithet for the influence preachers exerted in support of the Patriot cause. Advocates of the British crown found preachers’ support of the Patriot cause particularly detrimental to their efforts to maintain loyalty among the colonists. Such clergymen provided sanction for the cause of independence as well as formal support for the military effort. In the 1770s, most colonists still considered themselves aligned with England; many parishioners questioned the fundamental legitimacy of revolution, and of separating from Britain and consequently the Church of England. From their pulpits, these members of the Black Robe Regiment reassured their audiences that their revolution was justified in the eyes of God. Winning and maintaining the support of the population was critical in the American War for Independence, which relied heavily on the support of volunteers and the general population.

Peter Muhlenberg is perhaps the most iconic figure associated with the Black Robe Regiment. A Virginia minister, Muhlenberg accepted a commission to lead a regiment of the Continental army. An anecdote—likely apocryphal—from an 18th-century biography depicted Muhlenberg preaching to his congregation in his clerical robes, only to strip them off and reveal his military uniform underneath, a dramatic appeal for men to join the Patriot struggle. Muhlenberg served as an officer in the Continental Army throughout the war and commanded a brigade at the Battle of Yorktown. But Muhlenberg’s literal participation in the war’s fighting was highly unusual for clergymen. Far more common, and the origin of the British label “Black Robe Regiment,” was the rhetorical support for independence those ministers offered regularly from their pulpits. Nor should the undeniable importance of support from this influential group of Protestant clergymen suggest that the American Revolution was mainly a religious revolution, or that its supporters were monolithic in their faith. Colonial religious life was heterogeneous and reflected a diverse set of beliefs. Some Patriot supporters, like the Black Robe Regiment and their congregations, subscribed to Protestant faiths and read in the events of the war evidence that God favored their cause. Many other members of the founding generation—products of the Enlightenment, which emphasized reason and rational explanation over revealed truth—characterized themselves as Deists, believing that a divine God had created the universe and set it in motion, but took no active role in shaping or guiding human affairs. A few influential Patriots seemingly defied any sort of religious affiliation: Thomas Paine, whose pamphlets "Common Sense" and "The American Crisis" were credited with boosting support for the Patriot cause during critical junctures in the revolutionary movement, famously rejected organized religion and the creeds professed by various faiths. Asserting that “My own mind is my own church,” Paine suggested that the various religions appeared to him as “no other than human inventions, set up to terrify and enslave mankind, and monopolize power and profit.” Success in the War of Independence drew on Americans of diverse backgrounds, beliefs, and faiths, who unified effectively enough to defeat the world’s strongest military power in a bloody and protracted conflict.

While there are isolated instances of African Americans serving in the Confederate ranks, there is overwhelming evidence that this small number represents rare and exceptional cases: historian David Blight estimates that the number of black soldiers in the Confederate ranks was fewer than 200. That small number represents some partial companies of slaves training as soldiers discovered by Union forces after the fall of Richmond. One reason that only a handful of blacks fought for the Confederacy is that until the last weeks of the war, the Confederate Congress expressly forbade arming enslaved African Americans, who made up the vast majority of the black population in the South. Given white southerners' longstanding fears of a slave uprising (fears intensified by a few abortive attempts in the first half of the 19th century and exacerbated to the point of hysteria by John Brown's raid on Harper's Ferry in 1859), the acute resistance of Confederates to arming blacks is understandable. Putting muskets in the hands of enslaved African Americans presented more than simply a concrete threat—embracing the notion that blacks could serve as soldiers in the same fashion as whites threatened deeply-held Southern ideas of race-based honor and masculinity. As Confederate Secretary of State Robert Toombs put it, "The day the army of Virginia allows a negro regiment to enter their lines as soldiers, they will be degraded, ruined, and disgraced."

Northerners were scarcely more enthusiastic about arming African Americans than their Southern counterparts. For the first year and a half of the war, Abraham Lincoln's administration eschewed the enlistment of black troops, fearful of a public backlash. Not until Lincoln signed the Emancipation Proclamation on January 1, 1863, did the Union Army begin to enroll African Americans in its ranks; even then, the decision proved deeply controversial, particularly among Northern Democrats. The Confederacy did not seriously entertain the idea of arming enslaved African Americans until a full year later, when the war situation in the South had grown much more desperate. In January 1864, months after the defeats at Gettysburg and Vicksburg, Patrick Cleburne (one of the most successful combat commanders in the Confederate Army) circulated a proposal to arm the slaves. Northern successes on the battlefield, Cleburne argued, threatened the South with "the loss of all we now hold most sacred—slaves and all other personal property, lands, homesteads, liberty, justice, safety, pride, manhood." Sacrificing the first, Cleburne held, could save the rest; the Confederacy could check Union advances by recruiting an army of slaves and guaranteeing freedom "within a reasonable time to every slave in the South who shall remain true to the Confederacy." A dozen of Cleburne's subordinates backed his proposal.

To most Southerners, however, Cleburne's plan was appalling. The prospect of arming the slaves struck one division commander as "revolting to Southern sentiment, Southern pride, and Southern honor." A brigade commander suggested that accepting enslaved African Americans as soldiers would "contravene the principles upon which we fight." Sensing the potential for the debate to cause dangerous dissension within the ranks, Confederate President Jefferson Davis ordered the generals to cease the discussion. Debate over the decision to arm enslaved African Americans resurfaced many months later, as the Confederacy's situation grew progressively more dire both on and off the battlefield. When another similar proposal reemerged it carried the imprimatur of Robert E. Lee, commander of the Army of Northern Virginia and perhaps the most revered figure in the South. In February 1865, Lee wrote a letter to a Confederate congressman characterizing the plan as "not only expedient but necessary." Even with Lee's support, though, the bill proved deeply divisive. It was not until March 13, 1865, just weeks before Lee's surrender, that the Confederate Congress passed legislation allowing for the enlistment of black soldiers. The two companies discovered by Union troops after the fall of Richmond never went into battle. Opposition to African American soldiers was passionate on both sides. The notion of fighting alongside blacks violated many deeply-held beliefs of white Northerners and Southerners alike. In the Union army, African Americans served in segregated regiments under white officers; many were used for menial tasks rather than fighting, and those that went into combat suffered abuse from their white comrades and were often singled out as targets by their Confederate foes. Nevertheless, the vast majority of African American troops fought bravely and with distinction, and by the end of the war, their actions in combat had begun to change the assumptions of at least some of their comrades regarding the fitness of blacks for battle. Despite their demonstrated fighting ability, it was nearly another full century before the United States Army finally desegregated individual units.

I’m not sure how this question defines “great civilization,” but it seems that, like most other people educated in the United States, the questioner is unaware of the highly stratified, centralized, and elaborate societies that did exist north of the Rio Grande prior to the arrival of Europeans. We are taught that Indian societies in North America had no governments, class structures, religions, intellectual traditions, or other elements of what Western European philosophy calls “civilization.” But to contrast that view, I'll offer a few examples. I think we can fairly say that all societies, regardless of how elaborate their social and political structures may be, are “civilized.” The largest city in North America prior to 1492 was called Cahokia, located on what is today the Missouri River across from St. Louis. As a city-state, the population of 15,000 people was comparable to London or Paris at that time. Cahokia was the center of an elaborate trade network that stretched across the entire continent from 950 to 1250 AD. City residents, along with laborers from far away, traveled to Cahokia over the course of several hundred years to build enormous earthen mounds. The largest one is 15 acres around and is the largest earthen structure in the Western Hemisphere. These mounds—not unlike European cathedrals in spiritual or architectural significance—served as symbols of power for elite religious and political leaders. These leaders often lived atop the mounds to be closer to the sun, their spiritual source of power. The influence these leaders possessed was enormous. Not only could they command the construction of mounds, but they held the reins of the city's economic and military fortunes as well. Because of the extent of Cahokia's trade networks, the consequences of their decisions were felt all over the continent.

Another immense center of trade and spiritual power was located in Chaco Canyon in what is now New Mexico. Inhabitants and visitors to the canyon built 12 structures between 900 and 1150 AD, which had 200 or more contiguous, multistoried rooms and numerous “kivas,” or round, windowless areas that today the Hopi and Pubelo Indians (descendants of the people who built Chaco) use for worship. Like Cahokia, the labor required to build such structures must have been enormous and well-coordinated, evincing a sophisticated political, economic, scientific, and social organization. Surrounding these 12 structures were between 200 and 350 villages in the canyon. An estimated 15,000 people inhabited the area. Among archaeologists, two theories are popular about why Chaco was built. The first centers on trade and exchange. Archaeologists have found items from Mexico and Central America in towns and villages up to 60 miles away from the central part of the canyon, along with a system of roads. This evidence leads them to speculate that the Chaco structures were the center of trade, where people bought and sold goods. The second theory involves the scientific and spiritual dimensions of the buildings. The structures are built in line with astronomical movements of the sun, moon, planets, and stars, leading some to believe that it was in fact a kind of three-dimensional calendar, a much more elaborate version of Stonehenge in England. Settlers in the canyon would have gone there to worship at certain times of the year to be reminded of the order of the universe and their place in it. Ultimately, both these scenarios could exist. Certainly by anyone’s standards, a society that so fully integrated spiritual, scientific, and material aspects of life would qualify as a “great civilization.” If, however, by comparing North and South America you mean to ask why did North America not develop the exact same kind of societies that Central and South America did, then one answer to that may be population density. Central Mexico alone had 25.2 million people in 1491, making it the most densely populated place on earth. The whole continent of North America, by contrast, had 12–20 million people. As we see throughout human history and all over the world, higher numbers of people tend to lead to more highly stratified societies.