What's in a word? Depending on the word, plenty. Reams of historical and cultural association can be encompassed, with masses of implication for the story in which the word is used. In this case, the word is "dromond," which is used in ROTK, to describe the warships that make up the core of the fleet which comes to the rescue in the Siege of Gondor. What is a dromond? It isn't (for most households) a household word these days, after all.

Quick infodump: a dromond is a Byzantine warship. Due to the intervention of wars and the fall of empires since their day, there is not a lot of information about how they looked and were built, but what is certain is that they were a next-generation form of the classical bireme, the traditional war galleys of the ancient Greeks. They were big, and heavily armed: they carried catapults, (and occasionally, bronze arrays for spraying "Greek Fire," a category of napalm-like chemical weapons used in the early Middle Ages) on their decks. Later dromonds got rid of the typical "beak" array and instead of having a ram, replaced it with some kind of a boarding-plank setup around the prow, which could be run out or lowered making it very easy for soldiers to land quickly and in comparative safety when taking another ship or a town. Given that this is what the Corsairs in the books do, harry towns, and that there is no other major seagoing power for them to fight in the massive naval engagements of the Athens vs. Persia type, there is good reason to think that this would have been the case in the alternate timeline of Middle-earth as well.

Now, the rigging* of the Corsairs' ships is not described in the books. But there are reasons both internal and external why it is highly probable (and this probability should have been followed in the film) that they are square-rigged, rather than lateen- or lug-rigged. Square-rigging is the oldest form known, and is what Greek and Roman ships used, what Viking ships used, and what medieval/renaissance/baroque era ships in the west used. The lateen sail is triangular, similar to that of modern sailboats, and typical of ships found in Arab-influenced cultures. Thus, in our timeline, the later Byzantine galleys were lateen rigged. Now, although lateen was a fairly late invention in terms of boat building, it's possible to argue that it was a re-invention of something known in Atlantean times and afterwards forgotten, along with so many other things, like how to raise 50-ton monoliths.

However, in the account which Legolas and Gimli give of their adventures, they talk about having to wait for a favouring wind because they were not able to make much headway upriver without one. The advantage of the diagonal forms of sail  is that they can be angled to maximize any available wind and convert it to forward momentum, more easily than the square rig. Hence the fact that all modern racing boats use triangular sails of various styles. If the Corsairs used lateen, rather than square, they would not have had as much difficulty.

But, say you, there is a problem here, in that if they are truly the heirs of Númenor as well and masters of the seas of Middle-earth, shouldn't the folk of Umbar have figured out and be using such a configuration?

However, it is not so simple as that. No one thing is perfect in all situations — something which is easily forgotten in hypothetical arguments, and which is universally true. Square rig has more surface area, and allows for more power, which translates to bigger and/or faster ships. There are also difficulties in maneuverability with lateen-rigs, which are not present in square-rigged ships: the spar (the stick the sail hangs from) has to be taken down and switched over, so that the mast will not interfere with the expansion of the sail, to change course. This is slower than being able to simply pivot the spar right or left and have the sail expand forward, and makes it less practical to do what square-riggers do to enhance power, which is simply to 'crack on more sail' by having additional banks of canvas either above, or sequentially in line with, the mainsail. This is what the typical "Spanish Galleon" has, btw.

And, if you're not worried about labour costs, there are always the oars as an interim solution...

—Now, in the film, the ships of Umbar are black — but that's the only thing the filmmakers got right. They're not dromonds. They're not anything remotely like dromonds. (There were also, in the book, a host of other ships that came along, Dunkirk-style, volunteered by the rescued people of the coastal provinces, but that's irrelevant since the people of the coastal provinces were left out of the film, too; but they would likely have been cogs and caravels, fishing ships and small merchanters.) They look, in fact, like Malay pirate junks — a very different sort of ship, with a very different developmental history, and radically different set of associations. (More on that last, later.) They are, as it happens, lug-rigged, which is a wedge-shaped sail that has the angled advantages of the lateen-rig but allows for some more power due to the greater surface area of a trapezoid than a triangle, and was invented in the Far East. (Hence the use of a junk in a scene to immediately establish "this is China" in a picture.)

Now, what is the difference? You have, in the film, yet another example of "Asian" type enemies attacking purely "Nordic" type good guys, which is not unreasonably taken by many viewers as an example of racism on the part of Tolkien.** Careful readers have of course noted that the worst of the bad guys, like the Witch-King of Angmar, are also Númenóreans, who have gone over to the Dark Side in ages past; that Númenor fell because it turned Dark and trusted Sauron; that the Haradrim and other mortal allies of the Enemy are as much victims as the peoples against whom they are thrown away as pawns (evoking the use of colonial troops by European powers on both sides in WWI); that, in fact, the Corsairs themselves, the dreadful enemy who has ravaged the coastal provinces and allies of Gondor for generations — are themselves renegades from Gondor, those who split off in the Civil War that destroyed Osgiliath, and which was fought, in part, by those who were objecting to a rightful King whose Númenórean blood happened to be mixed with that of "native barbarians" —!

But given that plenty of book readers miss these nuances (like the neofascist Italian fans*** who have done great disservice to Tolkien over the years), and that the films have heretofore in the Theatrical Editions — which director Jackson assures us are meant to be the definitive editions, repeatedly, stating that the Extendeds are simply sops thrown to 'purists' to content them with extra materials that screw up his pacing — left them out entirely, this is not unreasonable for non-reader viewers to be troubled by it. And it was a case of the filmmakers' production decisions, not something required by the text itself.

—Because if they'd followed the text, you'd have had this image instead:

A black fleet of slightly-alien ships, both ancient and strangely futuristic, but recognizeably akin to those in our timeline associated with classical Greece and Rome, approaching a vast city, both ancient and strangely futuristic**** which is under siege in the approved classical manner, by armies and engines, and defended in the approved manner, by sortie and relief, and cavalry combat out on the plains before it by the largely black-haired, olive-skinned defenders as well as their blond barbarian allies. Does this begin to ring any bells among classics fans?

It ought to be setting off multiple alarms. Not just Rome and Carthage, or the Siege of Rhodes. Black ships at Troy, anyone? The Scythian Amazons riding to the attempted rescue of their ally Priam but being insufficient to win the day? Even the battering ram, Grond, which is fashioned in the form of the traditional cavalry mount of the Enemy, and bears the power, symbolic and real, of the ancient gods of the Dark, is a nod to older epic. (What, after all, brings down the Gates of Troy, I ask you?) And the conclusion of the story of Theseus and the Minotaur is also invoked in the book, very strongly: where the old lord of the city-state, seeing the black sails of mourning, makes the natural assumption that they bring the bad news of the failure of the quest and the death of his son, (and their people's continued servitude and role as fodder for the enemy's Beast) and commits suicide in his grief. (I do hope the parallel is sufficiently obvious…)

And it would have been very much clearer that the Enemy, sometimes, Is Us. Which is, after all, the whole point of the story of Númenor's downfall, and its relevance to the War of the Ring.

**—Don't even dream of invoking the acronym "PC", btw, in any context (looking around for large stick) because the current usage of it to dismiss all questions of ethnic relations and civility in public discourse, as popularized in the last two decades by radio demagogues and newspaper "pundits" (a Sanskrit word, that, hah) is not merely engaging in empty rhetoric as a substitute for self-examination and critical thinking, but also demonstrating the user's utter ignorance of the history and true meaning of the expression "politically correct" (spots assegai hanging on the wall) — though with a certain fine if unintentional irony, it is true. So, (leaning on functional African war-spear) — go ahead, make my day…

***I've encountered these people elsewhere, the narrow-minded who filter LOTR  (as all else, like Scripture) through their ideological blinders, and then claim justification from their own truncated versions; but there is a peculiar Italian twist, with young neofascists adopting their faux-Celtic, faux-Nordic emblems in the name of Middle-earth and naming their groups after elements in Tolkien's writings, which has served in turn to strongly convince those who are not already fans and readers there, that it is indeed a fascist work.

****Another major problem in the filmic representation of the siege of Gondor is the misrepresentation of the City itself. It's way too small, and flimsy. Yes, I too was initially enthused back in '02 by the tantalizing glimpses of the models under construction, and the hazy twilight shots from the ramparts, teasingly vague and allowing one to imagine that it was going to be far more impressive; just as I was eagerly anticipating the richness of Rohan from publicity stills of banners and gold and the like. At least this time, after the disappointment of TTT-M I was prepared somewhat. But the books are explicit - Minas Tirith is one of the greatest human achievements, a huge city, too big for its dwindling population, and besides all that, it's built by the same people who set up Orthanc as a little observation tower on the far edge of their domain back in the day. It ought, having been built as a fortress, to be even more massive and imposing - and in fact in the book we are told that the outer curtain wall is made of the same material as the tower of Orthanc, obsidian-like, slippery and black, not white sugar cubes. Minas Tirith in the films is not much bigger than the hill of the Acropolis — it doesn't as far as I can work out from photos, even cover as much territory as the first city of Athens, back before it was rebuilt following the defeat of Persia. The walls, inner and outer, are not plausible, by comparison to existing defensive structures built by strong powers with vast resources and skills at stoneworking, like Krak des Chevaliers or the ruins of ancient cities in Azerbaijan as well as the former Roman Empire; the fortress-city of the heirs of Atlantis ought to at least match up to anything built by ordinary mortals in our own timeline—!