A few essential facts you have to know before deciding whether to watch “Medieval,” a fictionalized early 15th century account of the exploits of Czech hero Jan Žižk.

The knight, rebel and celebrated general who “never lost a battle” was famously-nicknamed “One-eyed Žižka.” Ben Foster plays him in the film, and when we meet the hero, he’s pre-eye patch. So, you know what’s coming.

The film features Michael Caine as a sage advisor to the Kings of Bohemia,  including King Wenceslas IV, who was heir to the post of Holy Roman Emperor. We get a few scenes of a perplexed looking Lord Boresh in a coach that’s under attack early on, and a couple of scenes late in the third act with Britain’s Cockney treasure. He earns his pay, but not in the middle acts.

And as anybody who’s ever seen a sword-fighting movie — pirates, Romans, Medieval knights, Tartars, Robin Hood — a villain has to bark “He’s MINE,” in the middle of a melee, at some point.

Stuntman and actor turned director Petr Jákl (he also did another Czech history tale, “Kajínek“) serves up a sturdy, intimate and two-fisted epic in the muted greys of the Golden Age of Leather, Wood, Stone and Steel.

“Medieval” slides down the slippery slope towards cheesy, and the third act has annoying gaps in the story and lapses in logic. But how many Medieval Bohemian chivalry and combat stories make it to the screen?

Foster plays a fierce fighter, sometime brigand and sword-for-hire in the future Czech Republic in the middle of the Papal Schism. There’s a pope in Rome and a French-approved “Antipope” in Avignon. Wenceslas IV (Karel Roden) is in line to become Holy Roman Emperor, a “defender of the (Christian) faith position that began with Charlemagne and ended in the early 19th century.

But feckless Wenceslas has a rival brother, Sigismund (Matthew Goode, as slippery as one would expect), King of Hungary, and a lot of debts — mostly held by Henry of Rosenberg (Til Schweiger).

Lord Boresh (Caine), who retains Jan Žižk and his Bohemians as paid extra security, will need their help getting Wenceslas to Rome without incident, as Boresh sees this as the only way to mend the papal schism and rally Christianity against the Turks, or the Poles or heretical Eastern Orthodox Byzantines.

Those who would stop this include Rosenberg and his ally, Sigismund. The best way to foil Rosenberg and perhaps raise ransom cash for good-and-broke-King-Wenceslas might be kidnapping the fair Katherine (Sophie Lowe of “Blow the Man Down” and TV’s “Romper Stomper”). She’s the niece of the French king and engaged to the cruel Sigismund.

“Medieval” becomes a bloody game of “Who’s Got the Princess?” as rivals kidnap, battle over, “free” and recapture the Lady Katherine many times.

We see how “One-eyed Žižka” earned his nickname, and sample medieval treatment for open sores (not for the maggot-squeamish). We glimpse the tactician and combat innovator that Žižka is known to have been — turning wagons into rolling forts, a precursor to Žižka later arming them with cannon and inventing the tank.

Jákl’s script leans heavily on combat movie cliches translated into the age of lance, bow, shield and sword. There’s a sharpshooter — a guy who’s aces with a crossbow — a big cuddly hulk, a treacherous colleague and a super-sized knight-villain (Roland Møller).

Foster is quite good in a role that needs him for action more than line-readings or great displays of emotion. Goode and Schweiger offer decent support, and Caine does well enough with a somewhat thankless part.

Lowe doesn’t give the film the emotional punch her part called for, and frankly that’s not Jákl’s fault. He gives her chances, and she never manages to be much more than a placeholder in a role that is mostly fictional invention, although there was a real Katherine mixed up in these lives.

The third act shows signs of heavy-handed editing as we wonder how this character got tied to a tree and that one impaled by an arrow.

Still, it’s all perfectly workmanlike, save for the fights, which are splendid. If Medieval Times are your jam (as they are mine), “Medieval” is worth a look and almost entertaining enough to get by.

But what it’s “getting by” isn’t just corny tropes of films of the period, but way too much historical clutter and intrigues — almost Byzantine in their twisty complexity — to let this action picture every break free of the muck it’s stuck in too much of the time.

Rating: R for strong and grisly violent content throughout, and some nudity.

Cast: Ben Foster, Sophie Lowe, Matthew Goode, Til Schweiger, Roland Møller and Michael Caine.

Credits: Scripted and directed by Petr Jákl. An Avenue release.

Running time: 2:05