KIEV, Ukraine—Dusk envelops a Kiev industrial estate. A man in military camouflage brandishes a knife and lunges at Aleksandr Maksimtsov. Two seconds later, the attacker is pinned to the ground, his face pressed against a concrete slab.

“My goal is to turn my enemy into my friend,” says Maksimtsov with a benign smile, digging his knee into the man’s back. “Of course I can wound him, or kill him, but that is not my objective.”

He looks down at his chastened assailant. “Now I ask him, ‘Why did you attack me? Because you have no money? You’re hungry? OK, I call pizzeria— hello, pizzeria? Bring us cola and pizza.’ ”

A group of camo-clad students stands around the pair. They nod in approval at 52-year-old Maksimtsov—a former Soviet police colonel, now fighter guru—who has dedicated his life to preserving the secret martial art of the USSR.

It is called Systema (“the System”), a little-known combat method that can be traced back to the Cossacks of medieval times and was later used by KGB agents and Soviet Spetsnaz (special forces). Some Russian spy units are said still to draw on the practice today. It focuses on hand-to-hand grappling and weapon disarmament, emphasizing the importance of intense Zen-like calm to turn an attacker’s strike against him, coolly and effortlessly.

Most evenings, in an overgrown courtyard among a warren of warehouses, Maksimtsov meets with his students. They are a motley bunch that includes IT technicians, factory workers, and soldiers from Ukraine’s eastern warzone. Here, they shed their 9-to-5 civilian skins and enter a different world.

Despite their shared passion for this martial art, the group is not fully unified. The master sees himself as a product of the Russky Mir (“Russian world”)—a Slav with no time for divisive politics. His students, by contrast, are diehard Ukrainian nationalists from a new generation at war with Russia.

It’s an odd combat style to observe. There’s quite a lot of slapping and swaying. At other times, Maksimtsov exhibits raw power combined with fluid agility. Systema advocates a straight-edge lifestyle and instructs fighters to discard ego, fear, and tension in the heat of combat. In its purest form, this martial art is non-competitive and doesn’t rely on belts, grades, or titles. These Systema practitioners lie somewhere between Matrix-style fighters and weekend warriors.

“You have to live it,” says Maksimtsov, a giant at 6-foot-4, whose outward lankiness belies an explosive inner strength. “It’s not possible just to study Systema. You have to experience it.”

Even before we met, it was clear that Maksimtsov was quite the character. During an exchange of emails, he ended each message with a quirky proverb written in bold: “The master is not the one who runs fast but one who runs out early”; “Either I find a way or I’ll create it”; “A person without knowledge is the same as a mushroom: it looks strong but the ground does not hold well.”

We met in the Ukrainian capital, but his roots lie further afield. Born in 1965 in the Kazakh Soviet Socialist Republic, Maksimtsov spent his teens learning to box and wrestle in between grueling shifts at a coal mine. “During that time, I realized what hell was,” he says. “You are stuck in a tight hole. Water is up to your knees. The machine makes a howling sound. You breathe in dust so thick you can barely see your hands.”

His grandmother, from Ukraine’s Poltava region, and his grandfather, from the Russian city of Voronezh, had been deported by Stalin to this distant steppe. “Thousands of people were sent there. Many people died,” he says. “Survival was necessary—it was a very difficult time. But during my childhood, I thought I was living in the happiest nation in the world. Our minds were closed.”

At the end of the Brezhnev era in 1982, Maksimtsov was conscripted into the Soviet army where he first encountered Systema, a martial art shrouded in secrecy.

“There was one soldier who told me to attack him with my fists, then with a knife, and then with a wooden pole,” says Maksimtsov. “I just couldn’t do anything to him.”

A few years before the breakup of the Soviet Union in 1991, Maksimtsov left the army and joined a Ukrainian police unit targeting violent criminal gangs. One day, while reading a sports magazine, he came across a piece about “Russian ninjas” who used Systema, the martial art he had encountered years earlier as a soldier. This prompted him to find his own teacher and take up the discipline.

“There was one soldier who told me to attack him with my fists, then with a knife, and then with a wooden pole. I just couldn’t do anything to him.” — Aleksandr Maksimtsov

Over the ensuing decades—during which he became a police instructor and joined U.N. missions in the Balkans, the Congo, and Iraq—he developed his own style of Systema. Maksimtsov left the force in 2006 and began gathering around him a group of devoted followers. With his wife, Irina—a fellow Systema practitioner—he trains them in Kiev’s sprawling housing estates and derelict warehouses.

“My aim is to show people how to be more effective in life. Each person has their mission and Systema helps each person to find it,” he tells me before training. “When you control your body, you control your mind. And then you can control your surroundings.”

Once his students arrive, they form a circle, squat down and balance their elbows on their knees, palms upwards. Maksimtsov addresses them: “Relax your facial muscles. Get rid of your masks. Get rid of your grimaces. Find a place where your head rests naturally on the spine. Imagine how we pull ourselves up and grow as tall as we can. “

Their warm-up looks like a kind of Mad Max yoga: Most of the group is dressed in military fatigues. Slowly they stand up, stretch their arms, and descend into a downward-dog pose. Balancing postures and breathing exercises are followed by combat rolls and an hour of sparring drills, which involve immobilizing opponents with various submissions and throws.

Later in the training, Maksimtsov shows off his attack skills. Firstly, he hands me a hunting knife and tells me to stab him. I take a somewhat reluctant swipe. He deftly disarms me and presses the 7-inch blade against my stomach. Maksimtsov then instructs my photographer friend to stand still before walking toward him with a slow and pendulous gait, grabbing his throat with a tight grip, then kicking him in the groin. There’s no malice in the assault, but it’s an eccentric show of force.

These are just some of the moves in what is dubbed Maksimtsova Systema, one of several branches within this martial art. Precise details in the long evolution of Systema are hard to come by. But more recently, its development owes much to the work of two men: Viktor Spiridonov, a former officer of the Imperial Russian army, and Vasili Oshchepkov, a black-belt judoka who would later die in the gulag following one of Stalin’s purges. In the aftermath of the Bolshevik Revolution, the pair set themselves the task of creating the most effective style of hand-to-hand combat.

During the 1920s, they studied and synthesized various martial arts and wrestling techniques from around the world. This resulted in SAMBO, a Russian acronym standing for “self-defense without weapons” (SAMozashchita Bez Oruzhiya). Promoted as a national sport and adopted by military and secret police units, it offered Soviet authorities a new cultural practice that could unite the hundreds of disparate peoples living across the USSR.

As the Cold War intensified in the 1960s, Aleksey Kadochnikov—a former Soviet army officer regarded as the grandfather of Systema—further developed the Russian style of fighting. Drawing on the martial prowess of Russia’s ancient forebears, he began teaching his distinctive and dynamic style of close-quarters combat to military personnel at the Krasnodar garrison in southern Russia. Students were taught not to respond to force with force, but to thwart an opponent by absorbing strikes and deflecting blows with a constant gyration of the body. By turning an opponent’s strengths into weaknesses, it is not unlike judo. Russian President Vladimir Putin, of course, is a committed practitioner of that Eastern martial art, apparently drawing on its tenets not only when fighting on the mat but also while ducking and diving in the global political arena.

When the Iron Curtain lifted, Systema emerged from the shadows. Spearheading its dissemination were Mikhail Ryabko, a former special-ops commander with the Russian army, and his colleague Vladimir Vasiliev, who in 1993 founded a Systema school in Canada, the first one outside his native Russia.

“Systema is the modern branding, if you like,” says Matt Hill, a former officer with the British army’s elite Parachute Regiment, and now a Systema instructor who studied under Ryabko and Vasiliev. “Before them, it was known as the ‘Russian fighting system’ or ‘Russian martial art’, which goes back to ancient times, when the monasteries were guarded by warriors. Compared with Asian martial arts, it was very versatile and freestyle, and not coded by techniques or nomenclature.”

While Systema has some overlap with SAMBO, they are regarded as two distinct disciplines. Systema is ideal for operating decisively and discreetly in busy, urban environments. “SAMBO is about fighting another guy in a ring,” adds Hill.

Twenty-five years since Systema was introduced to the West, the same tense geopolitical climate that fostered its Soviet-era creation is returning. Today’s new generation of devotees includes Piotr Petrovelikiy, an unassuming 47-year-old who works in computer security—here tonight for training in these Kiev backstreets.

For him, Maksimtsov is something of a mentor.

“He is like a father to us. He has taught me how to cope with difficult situations in my life, in my work, with my wife and children. He is our guru,” says Petrovelikiy. “My goal, simply, is to survive—this is what every person wants. I’m happier when I’m alive.”

Along with the psychological benefits of Systema, there is also a strong sense of survivalist machismo among these men. “I do this to protect myself and my relatives,” says one of Petrovelikiy’s fellow fighters, a 22-year-old Ukrainian army lieutenant who gave his name as Ivan. “Everything is changing, everybody is changing. The world is getting crueler. If you’re not a cruel person, you have no chances for survival.”

I ask Ivan if he’s ever used his combat skills for real. “I’ve never had the opportunity, thank God,” he replies. “But, if I did, it would end badly for the other person.”

Despite the fears and escapist fantasies that have led these men to take up Systema, Maksimtsov is less paranoid. He avoids talk of division even as the relationship between Russia and the West plunges to an icy low.

“I don’t see a big difference between Americans and Russians,” he says. “And Ukrainians and Russians are the same Slavic people. Everyone in the world has similar aspirations. We should achieve these goals together, not separately. Always you must communicate. Everybody knows that the best kind of fight is the one that never happened.”

Then again, Maksimtsov knows that the readiness is all.

At the end of the session, before heading into the Kiev night, he turns to me and bids farewell, summoning his inner Sun Tzu: “This is what I believe—better to be a warrior in a garden, than a gardener in a war.”