“The Great War of Archimedes” is World War II history with a twist — several twists.

It’s about mathematics, an “Imitation Game” and “Fat Man and Little Boy” tale of a lone genius whose calculations, estimating the “real” cost of the world’s biggest-ever battleship, could change the course of history.

“Archimedes” is also Japanese, and it’s speculative fiction, based on a manga (comic book) that ponders a fascinating “What if.” As in “What if Japan’s decision to build the super-battleship Yamato was a big reason the country was so eager to swagger into war” with countries (the U.S. and Britain) that were sure to out-produce, outnumber and overwhelm them in the end?

As our hero here, the “once in a century” mathematical mind named Tadashi Kai (Masaki Suda) puts it more than once in the film, “Numbers never lie.”

He’s a headstrong, on-the-spectrum and OCD genius who was kicked out of Tokyo University, but whose way with numbers, formulae and “measuring” and extrapolating make him THE guy Admiral Yamamoto (Hiroshi Tachi) calls on to debunk a bogus cost estimate for the ship pitched by its designer, Admiral Hirayama (Min Tanaka).

It’s 1933, and Japan, out of the League of Nations and increasingly a rogue state to the rest of the world thanks to its invasion of Manchuria and increasingly militaristic belligerence, must decide how to replace an obsolete battleship.

Yamato says (in Japanese, with English subtitles) “Forget battleships,” they’ll be “useless” in “the next war.” He and Admiral Nagano (Jun Kunimura) lobby hard for a new aircraft carrier.

But the Old Guard of the Imperial Navy, led by Admiral Shimada (Isao Hashizume) want to sink the taxpayers’ yen in this “beautiful” showpiece battleship — fast, heavily-armed and armored. Airplanes? Those two-winged (still) fragile little things? They couldn’t touch it.

When Kai gets the pep talk that alters his anti-patriotic mindset (he’s anxious to emigrate to America), how the hubris this ship gives the navy and the naive public could lead to war, he sets out to figure out the true cost of the ship, which any novice can tell would cost quite a bit more than its designer claims.

The quest becomes a thriller as navy factions smear Kai, his not-quite-girlfriend (Minami Hamabe) and stonewall the newly-appointed Lt. Commander and his aide (Tasuku Emoto) at every turn as they scramble to gather the data they need to make an informed estimate when everything about this unnamed “monster” of a warship is “classified top secret.”

There’s a deadline, of course, which gives “The Great War of Archimedes” (named for the great ancient Greek mathematician) a “ticking clock,” counting down the fate of our heroes and the world.

Writer-director Takashi Yamazaki (“The Fighter Pilot”) makes this mad dash for military math suspenseful and pretty entertaining. Kai’s fetishized measuring tape — When we meet him, he’s measuring a the faces “etc.” of a bevy of geishas. — comes in handy as he dashes from ships to shipyards, doors slamming in his face as he keeps jotting down numbers — length, beam (width), number of rivets per metric foot of steel.

Yamazaki also makes the debates in the naval committee tense and riveting. Lots and lots of that particularly Japanese brand of bellowing, harrumphing and taking umbrage.

The film opens with an impressive digital recreation of the April 1945 sortie that sank the Yamato, a beautifully-rendered battleship assaulted by a swarm of U.S. Navy Helldiver dive bombers and Avenger torpedo bombers. It’s brilliantly detailed — screaming gun crews blazing away and dying, the ship taking hit after hit after hit, finally rolling over and sinking as a sea of extras drown or burn to death.

If anything, the movie understates how difficult the “Yamato Class” battleships (there were two) were to sink.

There’s also a shakedown cruise scene set on an early Japanese carrier, launching biplanes and other scenes set on battleships not at war.

This isn’t a conventional war movie, more of a superficial gloss of “How we blundered into war” tale, complete with Japanese revisionist scrubbing of how their “advance into China” (a bloody, territory and resource-coveting invasion) history.

But it’s a very entertaining and offbeat spin on Japan’s pre-WWII history and the national mood at the time, and an intriguing if somewhat far-fetched “what if” about the country’s long, delusional journey into World War II.

MPA Rating: unrated, violence

Cast: Masaki Suda, Hiroshi Tachi, Minami Hamabe, Tasuku Emoto, Min Tanaka, Isao Hashizume

Credits: Scripted and directed by Takashi Yamazaki, based on the manga by Norifusa Mita. A Well Go USA release.

Running time: 2:09