“The Ministry of Ungentlemanly Warfare” does well with its “Superman and Reacher kill Nazis” vibe before overcomplicating the matter. Yet the biggest issue with director Guy Ritchie’s World War II action comedy is it doesn’t know what kind of movie it wants to be.

On one hand, it pairs one-liners and cartoonish violence with the men-on-a-mission trope seen in everything from “The Dirty Dozen” to “The Suicide Squad.” At the same time, “Ungentlemanly Warfare” (★★½ out of four; rated R; in theaters Friday) is based on a true story, with real-life figures peppered throughout the mayhem, which seems to keep it from fully being a devil-may-care romp. Thankfully, Henry Cavill and Alan Ritchson – the aforementioned cinematic Man of Steel and “Reacher” stars, respectively – are there to gleefully macho up a fitfully enjoyable lesson in British espionage history.

Loosely based on a 2014 Damien Lewis book, “The Ministry of Ungentlemanly Warfare” is a fictionalized tale of the crew of agents who worked in an unofficial capacity for Winston Churchill, England’s wartime prime minister, as part of his Special Operations Executive. (The details of their work, contained in Churchill's confidential documents, were declassified in recent years.) 

In 1942, dangerous German U-boats rule the Atlantic Ocean, keeping America from joining the European front, and Britain is reeling. Brigadier Gubbins (Cary Elwes) enlists the help of incarcerated soldier Gus March-Phillipps (Cavill) to lead an unsanctioned effort to the coast of West Africa to blow up an Italian vessel used to resupply Nazi submarines.

If British forces catch them, they'll be put in jail. If Nazis catch them, well, that'd be much worse.

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Gus gets to choose his own group of roustabouts and ne’er-do-wells, including beefy “Danish Hammer” Anders Lassen (Ritchson), demolitions expert Freddy “Frogman” Alvarez (Henry Golding), young Irishman Henry Hayes (Hero Fiennes Tiffin) and ace planner Geoffrey Appleyard (Alex Pettyfer), who they first have to break out of a Nazi prison camp. 

Their journey involves a bunch of bullets and arrows and a high German body count – one bloody episode has Ritchson’s character doing a “Weekend at Bernie’s” routine with a Nazi officer’s corpse. Their assignment goes awry at key points, though the band of miscreants also has a pair of undercover agents on their side, Heron (Babs Olusanmokun) and Marjorie Stewart (Eiza González). Marjorie is a singer, actress and quite the crack shot but instead of shooting up stuff with the main dudes, her primary job is to Mata Hari a Nazi officer (Til Schweiger) at a party while the prime-time subterfuge is happening.

When it’s cooking, “Warfare” offers some really good action, but it’s hamstrung by too many subplots and a large cast. The hallmark of Ritchie’s early work (“Snatch,” “Lock, Stock and Two Smoking Barrels”) was its array of colorful personalities – that’s not the case here, where even an iconic old bulldog like Churchill (Rory Kinnear) seems sort of bland. That aspect is at least where Cavill and Ritchson shine, giving their guys a winning, over-the-top verve. (Cavill, no stranger to impressive facial hair, boasts a gravity-defying handlebar mustache that does half the work for him.)

There’s an intriguing James Bond theme at play as well, with 007 author Ian Fleming (Freddie Fox) as one of the British intelligence officers, Gubbins having the nickname "M," and the real-life Gus being an inspiration for the iconic superspy. But “Ungentlemanly Warfare” riffs more on Quentin Tarantino’s “Inglourious Basterds,” from the spaghetti Western-ready music to its Nazi-butchering bent.

That movie at least fully owned what it was: an alternate-history revenge fantasy. With its blend of fact and fiction, “Ungentlemanly Warfare” is less confident and it shows because musclebound chaps doing murderously madcap work can only go so far.