Thirteen years ago, John A. Tvedtnes wrote a thoughtful article titled "Book of Mormon Population Statistics." Here's the link:
He begins the article with this observation.
Readers of the Book of Mormon sometimes think of Nephite and Lamanite populations in terms of millions. In fact, only the Jaredites are ever said to have numbered in the “millions,” and only at the end of their history, when we read that nearly two million men had been slain with their families (Ether 15:2).
Two million men is an enormous number. The total of all wartime deaths of Americans from the Revolutionary war through the present (over 200 years) is only around 666,000. It does not seem plausible that two million Jaredite men were "slain by the sword" in any short period of time.
I prefer the interpretation that Coriantumr was reflecting on the cumulative total of his people who "had been slain by the sword" up to that time; i.e., from the beginning of their chronological history. It makes more sense in context, given the continual stream of prophets warning the people, followed by wars and destruction. This interpretation flows naturally from a careful reading, although of course other interpretations are also possible.
Ether 7 records several times when one group "gave battle" to another. Often these battles were preceded by prophetic warnings.
23 And also in the reign of Shule there came prophets among the people, who were sent from the Lord, prophesying that the wickedness and idolatry of the people was bringing a curse upon the land, and they should be destroyed if they did not repent. (Ether 7:23)
In Ether 8, there are more battles and destruction.
In Ether 10, we read that "Shez did remember the destruction of his fathers." (Ether 10:2) But soon enough, "there began to be war again in the land." (Ether 10:8)
Chapter 11 has many prophets prophesying about the destruction of the people, followed by wars and contentions, "insomuch that there was a great destruction, such an one as never had been known upon the face of the earth." (Ether 11:7)
We know about this history only because records were kept, which Moroni abridged. Those records undoubtedly included details about how many people died.
Chapter 12 introduces Ether. "And Ether was a prophet of the Lord; wherefore Ether came forth in the days of Coriantumr, and began to prophesy unto the people, for he could not be restrained because of the Spirit of the Lord which was in him. For he did cry from the morning, even until the going down of the sun, exhorting the people to believe in God unto repentance lest they should be destroyed, saying unto them that by faith all things are fulfilled— " (Ether 12:2-3)
Years later, after more wars and destruction, we read:
1 And it came to pass when Coriantumr had recovered of his wounds, he began to remember the words which Ether had spoken unto him.
2 He saw that there had been slain by the sword already nearly two millions of his people, and he began to sorrow in his heart; yea, there had been slain two millions of mighty men, and also their wives and their children. (Ether 15:1–2)
This looks to me like Coriantumr was reflecting on what Ether had told him. Looking back over the history of his people, Coriantumr saw how many times the prophesies had been fulfilled, and how many of his people had been slain by the sword as a result. Over the 33+ generations of history in the New World, accumulated battle deaths of two million are not only plausible, but realistic in light of human experience in other parts of the world.
What were the words Ether had spoken to Coriantumr?
2 For behold, they rejected all the words of Ether; for he truly told them of all things, from the beginning of man; and that after the waters had receded from off the face of this land it became a choice land above all other lands, a chosen land of the Lord; wherefore the Lord would have that all men should serve him who dwell upon the face thereof. (Ether 13:2)
Ether rehearsed the entire history of the Jaredites, which explains why Coriantumr would be reflecting on that history.
20 And in the second year the word of the Lord came to Ether, that he should go and prophesy unto Coriantumr that, if he would repent, and all his household, the Lord would give unto him his kingdom and spare the people—
21 Otherwise they should be destroyed, and all his household save it were himself. And he should only live to see the fulfilling of the prophecies which had been spoken concerning another people receiving the land for their inheritance; and Coriantumr should receive a burial by them; and every soul should be destroyed save it were Coriantumr.
22 And it came to pass that Coriantumr repented not, neither his household, neither the people; and the wars ceased not; and they sought to kill Ether, but he fled from before them and hid again in the cavity of the rock. (Ether 13:20–22)
Despite Ether's warning, the wars continued for several years, culminating in the week-long battle at Cumorah.
But even there, at Cumorah, if we extrapolate backward the numbers given in chapter 15, the total number of people involved is fewer than 10,000, which corroborates what Oliver Cowdery wrote in Letter VII. He said "thousands" of Jaredites died there.
The article helpfully includes all the passages from the Book of Mormon that relate information about population size. Tvedtnes reaches this reasonable conclusion: "In none of these instances can one make a case for millions of people calling themselves Nephites or Lamanites."
In his last paragraph, Tvedtnes explains that "Prior to the time of Mormon, the largest numbered army in the Book of Mormon comprised 10,000 soldiers, in the time of Helaman. Only during the last Nephite-Lamanite wars do we read of armies numbering 30,000 and more. It is possible that some of the earlier “numerous hosts” comprised tens of thousands of men, but this cannot be ascertained from the information given. In no case is there any evidence of “millions” of either Nephites or Lamanites."
Even in the days of Mormon, his largest enumerated army was forty and four thousand. And this was after gathering the people together.
6 And we marched forth and came to the land of Joshua, which was in the borders west by the seashore.
7 And it came to pass that we did gather in our people as fast as it were possible, that we might get them together in one body....
9 And now, the Lamanites had a king, and his name was Aaron; and he came against us with an army of forty and four thousand. And behold, I withstood him with forty and two thousand. And it came to pass that I beat him with my army that he fled before me. And behold, all this was done, and three hundred and thirty years had passed away. (Mormon 2:6–7, 9)
This was in the year 330. Fifty-four years later, in the year 384, after a continual retreat from the Lamanites and scenes of blood and carnage, Mormon says they again "gathered in all the remainder of our people," this time "unto the land of Cumorah." (Mormon 6:5)
Some people think the text says 230,000 Nephites died at Cumorah. Maybe so. Maybe despite the warfare, destruction, and retreat, the Nephites managed to grow their population to support an army five times as large as Mormon managed to assemble when he gathered the people together 54 years earlier.
But that does not seem plausible to me and it is not what the text requires.
In my view, Mormon wrote his final words in a state of reflection comparable to Coriantumr's, thinking back over his lifetime as a military leader and all the soldiers who died under his command, with their respective leaders.
In the following passages, Mormon explains that he could see the "ten thousand" of his people led by him, plus the "ten thousand" led by Moroni. We cannot tell if these were literal numbers or "ten units" or "ten squads" of men, which could be the case if the plates had a term similar to the Hebrew word which means both a specific number and a military unit.
Oliver Cowdery, in Letter VII, said there were tens of thousands of dead bodies in the valley, presumably meaning both Nephites and Lamanites. That's consistent with the text when we realize the distinction Mormon made between describing what he saw (did behold, beheld) and what he reflected upon (behold). In the following passage, "did behold" and "beheld" are past tense forms of the verb "behold" meaning "see" or "view."
But the term "behold" in verse 13 is an interjection, meaning a word used to express strong emotion. Mormon used that term many times to mark a lesson drawn from history.
11 And when they had gone through and hewn down all my people save it were twenty and four of us, (among whom was my son Moroni) and we having survived the dead of our people, did behold on the morrow, when the Lamanites had returned unto their camps, from the top of the hill Cumorah, the ten thousand of my people who were hewn down, being led in the front by me.
12 And we also beheld the ten thousand of my people who were led by my son Moroni.
13 And behold, the ten thousand of Gidgiddonah had fallen, and he also in the midst.
14 And Lamah had fallen with his ten thousand; and Gilgal had fallen with his ten thousand; and Limhah had fallen with his ten thousand; and Jeneum had fallen with his ten thousand; and Cumenihah, and Moronihah, and Antionum, and Shiblom, and Shem, and Josh, had fallen with their ten thousand each.
15 And it came to pass that there were ten more who did fall by the sword, with their ten thousand each; yea, even all my people, save it were those twenty and four who were with me, and also a few who had escaped into the south countries, and a few who had deserted over unto the Lamanites, had fallen; and their flesh, and bones, and blood lay upon the face of the earth, being left by the hands of those who slew them to molder upon the land, and to crumble and to return to their mother earth.
When read this way, we have 20,000 people killed (or the people in 20 military squads or units, however many that was) in the valley west of Cumorah. The other enumerated 210,000 (or 210 units) were killed elsewhere, earlier in Mormon's lifetime during the carnage he described leading up to the final battle at Cumorah.
This interpretation of the text is consistent with the prior statements in the text about the size of the Nephite population. It is plausible in light of the archaeology and anthropology of western New York. And it fits Letter VII, which explains that there were tens of thousands killed at Cumorah, including Lamanites and Nephites, not hundreds of thousands.