Vladimir Putin is a colorful character.

Outside Russia, he’s cast as a villain. Inside Russia, it seems like he’s a hero. From the outside, he comes across as an enigma — tough but endearing, ambitious but patient, and mysterious but not really elusive— all at the same time. He started his career as a KGB officer, left to enter politics and rose rapidly through the ranks to become President of Russia, flew a Sukhoi Su-27 fighter jet as a presidential candidate in 2000, took a now-infamous shirtless ride through Siberia on a horse, and recently played the piano while waiting to hold trade talks with China’s president. And despite controversy, Time magazine named Putin its Person of the Year in 2007.

He also knows how to fight. Like, hand-to-hand combat kind of fight. He’s a black belt in judo, and has been practicing the sport since he was 12. He even published a book covering the sport’s history & technique in 2004, along with a 1.5-hour instructional video.

While it’s not unusual for a world leader to have published a book, it is unusual for a world leader to have published a book that isn’t somehow related to politics, history, or their own life (e.g., a memoir).

Here’s an excerpt from his book, Judo: History, Theory, Practice, in which Putin discusses a judo strategy for winning against a stronger opponent:

The meaning behind the Kodokan’s motto — “The Most Efficient Application of Strength,” as Jigoro Kano put it — consists of the following. Assume that a person’s strength is measured in some sort of units. An opponent’s strength is ten, yours is seven. If your opponent pushes you with all his might, you won’t be able remain standing, even if you resist with all your might. You’ll either fall or step back. This is opposing strength with strength. But if you give way to the extent that you are pushed, maintaining your balance and withdrawing your body, your opponent will stagger forward and lose balance. At that moment, weakened by this awkward position, your opponent is very vulnerable. You, on the other hand, by maintaining your balance, can use all seven units of your strength, to score a victory. “Give way in order to conquer.” The highest degree of judo mastery is the ability to give way in the name of victory. Let’s illustrate this tenet with the following example. Imagine you are a door and that you are locked shut; your opponent, however, is determined to break you open with his shoulder. If your opponent is big and strong enough and rams through the door (that is, you) from a running start, he will achieve his aim. Now let’s consider a different turn of events. Instead of digging in your heels and resisting your opponent’s onslaught, you time it so that when your opponent is just about to hit the door, you unlatch it. Then, not meeting any resistance and unable to stop, your opponent bursts through the wide open door, losing balance and falling. If at this time you raise the threshold slightly, “stick out your heel,” so that he trips (if we’re going to fantasize, let’s do it right), then victory will be unconditional. Minimum effort, maximum effect. Similarly, you can play with the lock when the door opens outward and your opponent pulls the door (that is, you) open. As soon as your opponent tries to jerk the handle, thinking he is going to break down the locked door, the lock is opened and he is sure to lose balance. If at this time we are able to take the handle off the door, as it were, then that person, who was counting on brute strength but met no resistance while groping with the void, will surely fall on his back.

Whether or not this particular concept is relevant for understanding Russia’s foreign policy strategy under Putin is anyone’s guess. But it’s a valuable lesson nonetheless, one that can be used in business, law, other sports, and beyond. One hears bits of it in Sun-Tzu’s Art of War:

Simulated disorder postulates perfect discipline, simulated fear postulates courage; simulated weakness postulates strength.

A weak fighter going against a strong fighter on the basis of strength alone will lose. That’s obvious. But what other approaches does a fighter have? Tinker, be creative, find another vertical, turn it into a weakness, throw the opponent off balance, and then go in for the kill—it’s a battle-tested approach (pun intended) for anyone who’s ever encountered a formidable competitor in life.

The book is increasingly hard to find, but used copies are listed on Amazon here.