History takes a beating in “300: Rise of an Empire,” and viewers get a pretty good pummeling, too. This loud, in-your-face sequel to “300” is another wacky, CGI-dominated, ultra-macho bloodbath, based on a second (as yet unpublished) graphic novel by Frank Miller, who continues his comic-book trashing of the second Persian invasion of Greece, moving on from the battle of Thermopylae at which Leonidas (Gerard Butler) and his Spartan host perished, to that of Salamis, where the Greek naval forces triumphed, but pausing to add a flashback to the battle of Marathon ten years earlier.

The hero this time around is the Athenian Themistocles (Sullivan Stapleton), portrayed by Herodotus—the basic historical source—as a wily, manipulative politician but here transformed into a brawny Braveheart stand-in. According to this telling, Themistocles was the victor at Marathon, even killing the Persian king Darius (Igal Naor) with a miraculous long-distance arrow shot. (In truth, though Themistocles was one of ten generals at Marathon, the victory was the work of Miltiades and Callimachus, and Darius wasn’t even there. His forces were commanded by a general named Datis.)

The task of subduing the Greeks eventually fell to Darius’ son Xerxes (Rodrigo Santoro), who in this telling takes on a superhuman persona by undergoing a rite of passage in the desert under the direction of Artemisia (Eva Green), an orphaned Greek who was brought up as a daughter by Darius and trained as his most skilled and ruthless warrior. (In reality, Artemisia was a Greek queen in Asia Minor who was in effect a Persian vassal—and a relative of Herodotus, who emphasized her role in the invading host, as well as her nobility and honor. And Xerxes was hardly the rock-star type weirdo portrayed here.)

Much of the action this time around is at sea, with Themistocles first besting Artemisia, but then being defeated by her, at what is presumably intended to be a depiction of the battle of Artemisium, fought roughly simultaneously with Thermopylae. (The battle tactics are ludicrously wrong, but so what?) That’s followed by Themistocles’ pleas to the widowed Spartan queen Gorgo (Lena Headey) to join the fight with her city’s fleet (Sparta was a land-locked city with meager naval power, of course) and bring the Greeks together in a single nation to defeat the invader.

After an abortive effort by Artemisia to seduce Themistocles—the occasion for a sweaty sex scene—there follows the decisive battle of Salamis, in which the Greeks triumph. Once again the depiction is nonsensical, since Themistocles’ strategy was actually to lure the much larger Persian fleet into the confined straits so that his smaller, more maneuverable triremes could ram the cluster of clumsier vessels; here it’s played out on a great expanse of sea that makes the victory due to Gorgo’s arrival, like a last minute cavalry charge on the waves. Of course, there’s a last-act face-off between Themistocles and Artemisia that never happened; she survived the battle and returned home with Xerxes’ favor, though in escaping an assault by a Greek ship she rammed a Persian vessel.

It should be clear from this that Miller, and the screenplay that Zack Snyder and Kurt Johnstad derived from his book, have retained only the barest of historical bones and fashioned a story of Themistocles and Salamis even more fanciful than the one than the original “300” told about Leonidas and Thermopylae. That’s really a pity, since the tale told by Herodotus might have made a compelling screen narrative. But setting all that aside, the question that remains is simply whether “300: Rise of an Empire” is entertaining in its own flashy, brainless way.

The answer is: not very. As directed by Noam Murro—whose only previous film, the clever “Smart People,” makes this one look dumb indeed—it’s an unremitting cacophony of noise, action and gore, replete with decapitations and garish splashes of blood (none of it helped by the 3D that darkens and muddies everything) and pausing periodically for someone to deliver pseudo-grandiose pronouncements. Technically it follows the pattern of its predecessor, with the actors combined with digitally-constructed backgrounds so that everything looks as artificial as a comic-book panel—though Murro and cinematographer Simon Duggan employ lots more camera movement than Snyder, who presented “300” more as a series of tableaux, did.

As for the cast, only Green, who camps it up mightily as Artemisia, makes much of an impression—it’s a totally over-the-top performance, but at least is energetic. By contrast Stapleton is rather a stick, though he exhibits impressive pectoral muscles, and Santoro again merely strikes a series of poses. There isn’t much that’s notable among the other Greek defenders of liberty; we get a father-and-son team called Scyllias and Calisto (Callan Mulvey and James O’Connell) who are obviously designed to represent sacrifice for the national cause, and the tragedian Aeschylus shows up in the person of Hans Matheson (Aeschylus actually fought at Marathon, but what the hey). Andrew Tiernan appears in heavy makeup to play the Greek Ephialtes, who betrayed Leonidas, but his face, a plastic mask, isn’t noticeably less animated than those of actors not so encumbered. Even David Wenham, a carryover from the previous picture, is surprisingly anonymous as Gorgo’s counselor Dilios. A bombastic score by Junkie XL churns away relentlessly, assaulting the ears as a complement to the film’s attack on the eyes.

With its video-game style, “300” attracted a substantial fan base, who will probably turn out for this sequel too. They’re likely to leave a mite disappointed, though not as much as anybody with the slightest knowledge of the real story behind the battle of Salamis, which was a lot more interesting than what you see here.