Welcome, as always, dear readers.
Here’s an interesting passage from Appendix A of The Lord of the Rings:
“The third evil was the invasion of the Wainriders, which sapped the waning strength of Gondor in wars that lasted for almost a hundred years. The Wainriders were a people, or a confederacy of many peoples, that came from the East; but they were stronger and better armed than any that had appeared before. They journeyed in great wains, and their chieftains fought in chariots.” (iv: “Gondor and the Heirs of Anarion”)
Even if you didn’t know that a “wain” is a kind of wagon,

the context would probably provide you with an image of one—although probably the best-known wain now would be the one in John Constable’s (1776-1837) famous 1821 painting, “The Hay Wain”.

(If you’d like to see more of Constable’s work, with those amazing skies, see: https://www.wikiart.org/en/john-constable/ )
Such wagons as these (and “wain” and “wagon” come from the same Old English word, waegn), however, seem a little small for a wandering people, and I imagine that Tolkien saw them as more like a Boer trekwagen (also called a “Cape wagon”)

which he might have seen in South Africa as a small child, or at least had noticed in some of the numerous images of the Boer War of 1899-1902 available in magazines of that period,

like this issue of The Sphere from March, 1900–

Another possibility is that he had seen so-called Conestoga wagons

either in illustrations or even in films of the American West,

(from The Big Trail, 1930)
where they were shown being employed in ferrying families onto the Great Plains or beyond.

This might explain the wain—but what about the riders?
Invasions from the East were a common feature in the late Roman era, when the Western Empire was gradually turning into a Germanicized world, with various Gothic tribes pushing into what were once Roman provinces and even into Italy itself.

And behind the Goths came the Huns, a nomadic steppe people,

who were stopped at the Battle of the Catalaunian Fields (also called the Battle of Chalons) in 451AD by a combination of Romans and Germanic allies.

Even before this, there had been Celtic movement along the borders of the growing Roman world in the last century BC. A major trek was that of the Helvetii, who attempted to move from what is now western Switzerland, but were stopped and pushed back in 58BC by Julius Caesar (100-44BC).

As a medievalist, JRRT would certainly have known about the Goths and Huns, and, as a schoolboy, he would have read (or suffered through) Book One of Caesar’s De Bello Gallico, with its well-known opening, “Gallia est omnis divisa in partes tres”—“All of Gaul has been divided into three parts”. There, in Section 3, he would have read that, prior to their invasion, the Helvetii
“constituerunt ea quae ad proficiscendum pertinerent comparare, iumentorum et carrorum quam maximum numerum coemere…” (De Bello Gallico, 1.3)
“decided to collect those things which would be suitable for their setting off—to buy up the greatest number possible of beasts of burden and of wagons…”
Carrorum—the nominative singular is carrus–is itself a Celtic word and Aulus Hirtius, Caesar’s lieutenant, who continued Caesar’s account of campaigns against the Gauls, says of them:
“magna enim multitudo carrorum etiam expeditos sequi Gallos consuevit…” (De Bello Gallico, 8.14)
“for a great number of wagons was accustomed to follow the Gauls, even [when]traveling lightly” (expeditus, often means “lightly-armed”, but can also mean “without baggage”, hence my less formal translation)
It’s unclear what such vehicles looked like. If they were carts—that is, two-wheeled vehicles—they might have appeared like this simple Roman one—

If a 4-wheeled vehicle, perhaps something like this—

Here, then, might be sources for Tolkien’s invaders, both wains and riders, but what about those leaders and their chariots?
Although there are a number of chariot burials found in France (more or less modern Gaul),

Caesar never encountered chariot fighters in his conquest—of Gaul. In his two brief visits to England, it was a different matter, however.

As he describes them:
“Genus hoc est ex essedis pugnae. Primo per omnes partes perequitant et tela coiciunt atque ipso terrore equorum et strepitu rotarum ordines plerumque perturbant, et cum se inter equitum turmas insinuaverunt, ex essedis desiliunt et pedibus proeliantur. Aurigae interim paulatim ex proelio excedunt atque ita currus conlocant ut, si illi a multitudine hostium premantur, expeditum ad quos receptum habeant. Ita mobilitatem equitum, stabilitatem peditum in proeliis praestant, ac tantum usu cotidiano et exercitatione efficiunt uti in declivi ac praecipiti loco incitatos equos sustinere et brevi moderari ac flectere et per temonem percurrere et in iugo insistere et se inde in currus citissime recipere consuerint.” (De Bello Gallico, 4.33)
“This is the method of fighting from chariots. First, they ride around in every direction and hurl javelins and shake the ranks in general with the terror of [their] horses and the noise of [their] wheels, and, when they have worked themselves in among the troops of cavalry, they leap down from [their] chariots and fight on foot. Meanwhile, [their] charioteers gradually retreat from the battle and so place [their] chariots that, if those [chariot warriors] may be pressed back by a large number of enemies, they may have an unimpeded mode of retreat for them. In this way, they display in battle the mobility of cavalry, the steadiness of infantry, and they accomplish so much by daily use and practice that they have become accustomed to control [their] stirred up horses in sloping and steep places and to direct and turn [them] quickly and [they have also become accustomed] to run along the chariot pole and to stand on the yoke and to take themselves back from there into [their] chariots.”

In a letter to his son, Christopher (28 December, 1944, Letters, 107), JRRT mentions another figure connected with these ancient Britons, Julius Agricola (40-93AD), who was involved in several stages of the Roman conquest of Britain in the 1st century AD. What we know about him comes almost entirely from the biography of him written by his son-in-law, Publius Cornelius Tacitus (c.56-120AD). In Book XIV of his Annals, Tacitus describes a revolt of some of the British tribes against Roman rule, those tribes being led by a haunting figure in early British history, Boudicca, queen of the Iceni.

(This is a famous statuary group, by Thomas Thorneycroft (1815-1885), erected on the Thames Embankment, basically across the street from Parliament, in 1902.)
And in Tacitus’ description of the moments before the final battle of the revolt, we might see one more possible inspiration for those Wainriders and leaders in chariots:
“at Britannorum copiae passim per catervas et turmas exultabant, quanta non alias multitudo, et animo adeo fero[ci], ut coniuges quoque testes victoriae secum traherent plaustrisque imponerent, quae super extremum ambitum campi posuerant.
Boudicca curru filias prae se vehens, ut quamque nationem accesserat, solitum quidem Britannis feminarum ductu bellare testabatur…” (Annales, 14.34-35)
“…and the forces of the Britons were rejoicing everywhere in their companies and troops, how much more numerous than other [such forces], and with such a fierce spirit that they were bringing with them their wives, as well, as witnesses of their victory, and were settling them in wagons, which they had drawn up at the extreme edge of the field.
Boudicca, riding in a chariot, with her daughters in front of her, as she had reached each tribe, was swearing that it was indeed the custom for Britons to fight under the direction of women…”
Gothic invasions turned France, Italy, and Spain, at least briefly, into Germanic-speaking worlds, muscling in on the local Romans. The Helvetii needed serious fighting to be driven back to their original homeland. And those chariots initially made Roman infantry very nervous (Caesar himself says that they were “pertubati novitate pugnae”—“shaken by the novelty of the [manner] of fighting”—De Bello Gallico, 4.34). Perhaps, with such models behind them, it’s no wonder that it took nearly a hundred years to defeat those Wainriders.
As ever, thanks for reading.
Stay well,
When driving your chariot towards the enemy, always circle them counterclockwise (a huge insult in Old Irish stories),

(A totally overthetop Angus McBride of Cu Chulainn–but fun–and the Cu himself was more than a little overthetop when he would produce the gae bolga.)
And know that, as always, there’s
MTCIDC
O