Kazuya Shiraishi’s “11 Rebels” is an often entertaining Samurai thriller that wallows in the conventions and tropes of the genre.

The conventions of Samurai thrillers and American Westerns cross-polinated so long ago that it’s hard to remember which culture’s action pictures invented what. “Rebels” has noble sacrifice and “official” treachery, a motley collection of outcasts battling impossible odds via swordplay and gunplay and that hoariest of cliches, “Let’s solve our problems with explosives.”

Hell, if it worked in “Rio Bravo” and scores of lesser American “horse operas,” which not in feudal Japan?

The tale is loosely inspired by events of the Boshin War, the brief 19th century conflict in which the Emperor asserted primacy over a coalition of isolationist shogunates and Japan joined the more modern West by virtue of a conflict that featured breech loading artillery, Gatling guns and samurai swords.

If you’re a Western filmgoer who thinks “Last Samurai” era, you’re not far off.

Imperial troops are menacing assorted domains, among them the Shibata clan, struggling to “pick the winning horse” in the conflict between Emperor and “The Coalition.”

A plan emerges to defend a mountain pass with a bridge long enough for negotiations to pick a side to ally with, and thus save the capital city of the Shibata from assault. As they’ll be conscripting troops to lend to whichever side demands them in the meantime, that pass will have to be defended by a few samurai, and some convicted murders.

The dashing Takayuki Yamada is Masa, a condemned man waiting for his head-sawn-off execution for stabbing the Shibata samurai who raped his wife.

The “Eleven” here include a defrocked priest, the madman Noro (Takara Sakumoto), a lad (Amane Okayama) charged with trying to flee to Russia to learn Western medicine, an Old Samurai (Chikara Motoyama), a prostitute (Kano Ichiki) and a hulking mass murderer (sumo-turned-actor Ryôta Oyanagi) who bellows out his rising body count as he slaughters.

A handful of samurai led by Irie (Shûhei Nomura) and Heishiro (Taiga Nakano) are put in charge of holding this pass and bridge until they get word that the town is safe or has switched sides or whatever.

If just one convict flees, they all lose the pardons they will be granted for undertaking this “suicide” mission. Guess which convict is most determined to run off? That would be the guy who killed a Shibata for raping his wife.

There are “Seven Samurai/Dirty Dozen” plot elements and sequences here, some of which are so over-familiar as to be merely mentioned or covered in a brief (fix up the ruined fort) montage.

The script includes intertitles to ID assorted shakers and movers among the real figures on the periphery of this “last stand.” But actual character names are passed on grudgingly, so apologies for leaving half the “11” out.

But the reason B-movies like this still play is the tried and true plot points that go down like comfort food to action fans. Characters get spotlight moments swinging their blades and trying to light their matchlocks (generations of firearms are featured) in the rain, living and perhaps even forming a brotherhood (with one sister) as they fate their fates.

The gimmicks of the plot take the form of somebody who used to work with the family fireworks business and somebody who recognizes what “black water” is and how it could aid the defense of the pass.

The fights are furious and bloody. Don’t get too attached to anybody. Or any body part.

The cliches and the character clutter — Who ARE the eleven and who are samurai? — dampen the fun as much as rain dampens gunpowder here. But “11 Rebels,” like “13 Ronin” or “Seven Samurai,” is an action pic that recognizes there’s safety in numbers. That way, not everybody has to make the “noble sacrifice.” Because we always want somebody around for the finale. .

Rating: unrated, graphic violence, dismemberments, beheadings, etc.

Cast: Takayuki Yamada, Taiga Nakano, Kano Ichiki, Shûhei Nomura, Riho Sayasi, Ukon Onowe, Yûya Matsuura, Chikara Motoyama, Takuma Otoo, Amane Okayama, Sadao Abe, Ryôta Oyanagi, Takara Sakumotoi and Shûhei Nomura.

Credits: Scripted and directed by Kazuya Shiraishi, scripted by Kazuo Kasahara and Jun’ya Ikegami. A Well Go USA release.

Running time: 2:00