In 1910, after decades of intrigues, provocations and double-crosses, Japan formally annexed Korea. For the next 35 years, Korea showed up on maps as part of Japan, its capital Seoul renamed Keijo, its royal family whisked away to Tokyo as hostages, its people force-fed a diet of Japanese nationalism.

Detective inspector Lee (Song Kang-ho) is a good-hearted cop, who finds his loyalties tested when his Japanese masters task him with hunting down the resistance. Rebel mastermind Che-san (Lee Byung-hun) senses that Lee is on the verge of switching sides, and lures him ever closer to an explosives-smuggling ring that uses an antique shop as a front. But will Lee wake up to the cause and join the rebels, or will he hand over his countrymen to his dastardly Japanese bosses?

Director Kim Jee-woon returns to his native land, after helming Arnold Schwarzenegger in The Last Stand, for a gory, uncompromising glimpse of the rise of the Japanese war machine and the fires of the Korean resistance. Known simply as “Spy” (Miljeong) in its homeland, his beautifully grim, smoky vision of 1920s occupation has been released abroad with a far more evocative title, reflecting both its look and its loyalties: Age of Shadows.

“I’m drawn towards double agents,” comments Kim, pointing to people with divided loyalties who “act in secret while surrounded by enemies, standing at the borders of their turbulent age.” His film is all the more remarkable for being inspired by history, most notably the rise of the “Heroic Corps” (Uiyoldan). With dynasties collapsing in both Korea and China, and the Japanese plundering treasures from both, the real-life Heroic Corps did indeed use the antiques trade as a means of importing weapons from across the border. They carried out targeted assassinations of Japanese troops, high-level collaborators and a vaguely-defined subset of “traitors”.

Several schemes were thwarted by the authorities, but their first success came in 1923, with the bombing of the prominent Bell Street police station in central Seoul. The bomber, Kim Sang-ok, fought his way through a police cordon around his home, and committed suicide after a costly gun battle on the slopes of Mount Namsan. This all adds a touch of gritty realism to the film’s depiction of revolutionary intrigues, most notably a prolonged set-piece as agents desperately try track the glamorous but iron-willed arms smuggler, Gye-Soon (Han Ji-Min), on the Shanghai train.

“I wanted to capture the image of people navigating a tightrope between supporting or resisting Japanese colonial rule,” says Kim, “and being swept up in the consequences of setting one’s foot down on either side of the line.” Although it’s pretty clear which side of the line he is on – the Japanese are presented as unrelentingly cruel, old-school baddies. It shouldn’t come as a surprise that Age of Shadows is a Korean initiative, rather than a Japanese one. For a former coloniser to depict the period for entertainment purposes would seem gauche and indiscreet – how many English films have glorified the Irish War of Independence?

Far too many Korean movies are obsessed with a fratricidal, traitorous motif seemingly inspired by today’s North-South divide. But Age of Shadows makes it clear that Korean allegiances have been split for far longer, with the colonial regime struggling to hang onto its collaborators and root out its rebels. Antique dealer Woo-jin (Gong Yoo) is a Lovejoy charmer, trying to win over his police tail with honeyed words, dressing to impress in another historical touch – “I was fascinated to hear that real-life members of the resistance, never knowing which day might be their last, dressed each day with style,” the actor reveals.

For director Kim, the film was a chance to capture not only the atmosphere of the era, but also the lives of the founders of modern South Korea. “On the day before we started shooting, I visited the former office of the Korean Provisional Government in Shanghai,” he recalls. “It was so small that the bathroom was located right next to the dinner table. I wanted to suffuse the film with the emotion I felt, learning about the struggles of independence fighters who endeavoured to reclaim the spirit of a people who had lost their country.”

Jonathan Clements is the author of A Brief History of Japan. This article first appeared in Geeky Monkey #20, 2017.