Invisible Architecture
Walking the martial path over the last 2 ½ decades, I’ve come to realise that the most crucial structures in martial arts are invisible. They aren’t the obvious stances or strikes, but subtle principles – a kind of architecture of space and time – that quietly support everything. One of the architectural pillars holding up martial arts is often referred to as kūkan. At first kūkan was explained to me as simply “space,” and many others would literally talk about “controlling the space”[around my opponent]; but Hatsumi Sensei – seems to have nudged towards a different translation where kūkan means “slack”, referring to a space in time. Over the years teachers such as Ed Lomax, Paul Masse, Rob Renner and Nagato Sensei helped me understand this more deeply, through their writing or conversations. I’ve come to see four living principles as pillars of this hidden architecture, with kūkan being one of them:
- Slow down (yukkuri)
- Create and control slack (kūkan)
- Fail forward
- “Hai, play!”
These ideas emerged gradually, in quiet moments on the mat, through casual words from teachers, reading various essays and books. They are subtle, often unspoken lessons that seep in over time. Let me share them with you as they were shared with me – like a quiet conversation in the dojo after most have gone home, when the real learning often happens.
Slow Down
One chilly evening in Noda, many years ago now, I can still remember vividly Hatsumi Sensei taking out a much younger, faster attacker. He barely seemed to move – in fact his posture looked almost relaxed, unhurried – yet his uke (partner) fell to the floor before their strike could land. It looked as though Sensei had slowed time down, entering a state of total calm that allowed him to act at the perfect moment. What the uke described was something like” first sensei was there, and I thought I got him, only for him to disappear at the last moment.” Later, during a Nagato sensei session I heard it literally, “yukkuri,” a request to slow down. It has taken me years to start to connect the two.
Why train slowly? Because slowness allows us to see. It softens the urgency of the ego, which wants to win, impress, prove, dominate. Slowness opens the space between stimulus and response. It gives us the chance to sense, feel, and be in relationship with the attacker rather than just react. Going slowly disrupts the habit of “doing” techniques. It allows the body to move from centre, not from anticipation. If we go fast, we force the body to catch up to the mind. If we go slowly, we let the body lead the mind. When we slow down, we widen the gap between stimulus and response, creating space for conscious choice rather than automatic reaction.
Neuroscientists like Viktor Frankl ("between stimulus and response there is a space") and Daniel Kahneman ("System 2" slow thinking) show that deliberate attention engages higher brain centres, like the prefrontal cortex, enabling reflection. Cognitive scientist Mihaly Csikszentmihalyi’s concept of flow connects here: when perception sharpens and self-consciousness dissolves, action and awareness merge into effortless, fluid movement — not reflexive, but deeply attuned. Theories like Penrose and Hameroff’s Orchestrated Objective Reduction even suggest that, at deeper levels, consciousness may tap quantum processes, where reality isn't fixed until observed. Slowing down may allow access to these subtler layers, giving rise to creativity, freedom, and non-linear outcomes. In essence, slowing perception expands awareness — cognitively, neurologically, and perhaps even at the fundamental level of existence.
This doesn’t mean fighting in slow motion for its own sake; it means attaining a high[er] level ability to respond to what comes at me, without hurry or tension. “When you move slowly in the encounter, you stop emitting intention,” as one teacher put it. In other words, by not rushing, you cease telegraphing your own moves and can read your opponent’s intent more clearly. Your calm creates a sensory opening – you can feel what’s coming and can respond, even to changes in real time.
Paradoxically, slowing down internally lets you move earlier, not later. A Japanese friend pointed out a wonderful nuance: the word kansoku (観測), meaning “observation,” sounds the same as kansoku (緩速), meaning “slow speed.” In essence, to truly observe, we must slow down. By slowing our breath and mind, we start to notice the subtle shift of an attacker’s shoulder or their balance shifting to take a step, the tell of their intent before a punch is thrown. We begin to act in the moment before the moment. Hatsumi Sensei used to remind us that the foundation of timing is reading the context or scenario correctly - in advance.
If you position yourself well and early, “you will encounter moments of free time in the fight” – in which you can reassess the scenario. I’ve felt this: when I manage to stay relaxed and wait just enough, the opponent’s attack almost seems to arrive slowly, giving me a cushion to respond. It’s a fleeting slack in time, that appears because I didn’t leap in too soon or overreact or go in with a pre-formulated idea for a response or a specific technique.
Of course, reaching this state requires painstaking practice. In training we first drill mechanics at normal speed, but as skill grows, we cultivate a kind of inner slow-motion. I remember, many years ago Seno Sensei running an exercise with us: he had us stand so close to the attacker that the first punch would hit us – then we would adjust our timing slightly earlier on the next attempt, and again, until we found the exact distance and moment to evade without rush. “Move out too late and get hit, then a little earlier, and a little earlier, until you can move slowly enough – at the perfect timing – to avoid the attack,” [it was translated, by a fellow student]: “If you never get hit during training, how can you possibly know how to fight for real?”
That lesson stuck with me. It taught me that yukkuri – moving with deliberate calm – is not about being lazy or passive. It’s about developing such an acute sense of the present, that to a frantic opponent you seem impossibly early, even prescient. As Hatsumi Sensei once explained in class, “You do not try to block your opponent’s attack. You feel his attack… It is not a question of strength or speed. It is all about control.” And that control begins with a quiet mind and unhurried eyes.
Create and Control Slack
In another training session, Hatsumi Sensei spoke about the importance of distance and positioning. He introduced the term kūkan – typically translated as “space” – but famously corrected us by saying kūkan really means “slack.” Ed Lomax, was there and later wrote about the revelation in a short but revealing essay on training: “Distance and correct positioning are entirely time-dependent,” Ed noted, “so simply calling it ‘space’ misses the point. Hatsumi Sensei’s translation of the word as “slack” made a lot more sense”. In a fight, being in the right spot at the right time creates a sort of slack – an opportunity, a breath. If you understand your opponent’s intent and align yourself optimally, you gain time within the exchange. For an instant the combat has a looseness to it: freedom of motion. That is the slack Hatsumi Sensei wanted us to grasp – a living, elastic interval that you can create and control.
I remember how Sensei’s eyes twinkled as he told us to give ourselves some yoyū (余裕) – a word meaning “leeway” or extra margin – both in fights and in life. He said people should “give themselves some slack in their lives,” not only literally more free time, but by being patient with their own progress and “allowing themselves to be happy.”
This was a profound expansion of the idea: slack is not just a physical or temporal gap, but a mental one. It’s the room to breathe, to not be overfull or overstressed. My friend Paul, who trained Japan for 30+ years once illustrated this with a simple image of a cup of soda. If the cup is filled to the brim, there is no slack – any movement will spill it. But a half-full cup has extra space to play with. In the same way, Paul said, yoyū – slack – is a needed concept so that we can move freely with our taijutsu. Too many martial artists, he warned, act as if they must do something constantly, filling every moment with effort.
But true freedom comes when you leave some of the cup empty. That emptiness (or yoyū) is potential – it’s adaptability. It means not committing too rigidly to a single technique or outcome. Hatsumi Sensei often used the phrase “chūto hanpa” (中途半端), which Paul explained does not mean doing things sloppily, but rather “not being stuck on one technique” – doing things halfway in form so you’re free to change and adapt. In other words, don’t fill the cup to the top; leave room to adjust. This slack in movement creates a playful flexibility – you can flow around the opponent’s force instead of meeting it head-on. During Pauls training, I constantly see him take the slack out of the opponent, stretching them, whilst keeping or creating slack in himself, and as such, the ability to continue to adapt and change, as the opponent gets wrapped up, so to speak.
Slack is something you can manipulate in your opponent as well. I’ve seen Hatsumi Sensei subtly break an attacker’s balance and mental focus – a feint here, a light pain there – to “reduce the opponent’s intent to zero.” The attacker’s will falters and suddenly they are the one with no time, no space. Meanwhile, for an instant, you have all the space in the world. All fights have a strong psychological basis, Ed wrote: “By maintaining a calm state, you give yourself the mental slack to react appropriately, which in turn puts you in a better position and creates free time. By destroying your opponent’s intent, you force them to reassess … which again creates some slack for you in the fight.” However, “creating slack is not enough… if you do not use this slack, it will become slack for your opponent,” he warned. This was an important lesson: slack is dynamic. It’s opportunity – and opportunity can shift. When you seize the slack moment, you control the fight’s rhythm. If you freeze or hesitate, that moment passes to the other side.
In practice, this principle felt like learning to breathe with the opponent. I had to learn to relax even under threat – keeping just enough tension to act, but not so much that I had no surplus of motion. It’s a delicate balance, like holding a sword with a light grip: firm enough not to drop it, loose enough to respond to impact.
Over time, I realised this idea of slack extended beyond physical combat: It’s a strategy for life. Give yourself slack – time to rest, time to reflect – and you can move faster toward your goals because you’re moving smoothly, naturally and without the resistance of frustration or burnout. Hatsumi Sensei even tied this to happiness, as if to say: Don’t strangle your life with too much tension. Loosen up and joy will have room to grow.
Fail Forward
One of the hardest lessons for any martial artist is embracing failure. In the beginning, getting hit or making a mistake bruises the ego more than the body. In sparring and drills, good teachers encourage us to push to the point of failure – to the edge of now, where we weren’t comfortable or certain. If we messed up, all the better, because that’s where the real learning happens.
I recall someone sharing a story from Nagato Sensei, who had a straightforward philosophy on this. During one session, a student was too tentative and avoided fully committing to a technique because he was afraid of the counterstrike. He stopped the student, turned to the whole class and said, “Training is a promise. You trust that your partner won’t hurt you, and you do so in return. Take things slow and practice properly… Just punch straight, and if your tori (partner) does not move at the right time and distance, he will get hit. And you, as uke, should not be afraid to be hit.”
He continued, “There is no shame in being hit. Even I, as I show techniques, am occasionally hit. This is a part of the learning process… In a real fight, you will be hit, and you must not be shocked by it. Being hit lets you know that you did something wrong and need to work on it until you get it right.” Hearing this was liberating. He essentially gave us permission to fail. In fact, he expected us to. If we weren’t getting hit now and then, we weren’t truly testing the boundaries of our timing and distancing. We’d be fooling ourselves with false safety.
Nagato Sensei even had a specific method to cultivate this resilience. When practicing a dangerous scenario like facing a sword bare-handed (muto dori), he advised us to start from a disadvantage. “Instead of starting too far away and trying to get closer,” he said, “it’s better to start too close (i.e. getting hit) and then move slightly further. That way you always create the correct feeling in the opponent (that they hit you).” In other words, begin at failure – where you actually get tagged – and then inch backward until you find the razor’s edge where you can just barely evade. That edge is the real point of learning. I admit, at first this approach is scary. Letting yourself be in a position to definitely get hit goes against all our instincts. But it conditions you to not fear the hit, and to recognize viscerally what too late feels like. Each time you fail, you adjust a little earlier, a little smarter. You fail forward, using the last mistake as the springboard for the next success.
Over time, I noticed my attitude toward mistakes change. Rather than frustration, a miss or a tumble in training sparked curiosity. “Ah, so that angle was no good – what can I change?” Hatsumi Sensei’s whole disposition made it clear that lightness was key – if you messed up and got thrown to the mat, you’d often hear him chuckle. Not in a mean way, but in genuine good humour, as if to say, “Isn’t it interesting what just happened? “Then you’d pick yourself up with a grin as well. The environment was one where failure wasn’t final; it was just another step. One senior gave me this advice: “If you’re going to fall, fall forward. That way you’re a little closer to your goal when you get back up.” Corny as it sounds, it stuck in my head. To fall forward in a technique means you were moving with full commitment – you didn’t freeze up. And that commitment, even if it results in a fall, carries you onward. In life too, every setback can teach something if we face it directly.
I remember a particular sparring exercise in which I kept getting caught by a sweep I thought I had figured out. After the third or fourth tumble, my partner (a veteran much my senior) clapped me on the shoulder. “Good,” he said, smiling, “now you’re really learning it.” I laughed, “brushing the dust off”, with a deep breath…we started all over again. He was right, though. Those failures had burnt the timing of that sweep into my bones in a way mere theory never could.
Growth happens at the edges of our comfort zone – the edge of now, the edge of failure – because that edge is real. It’s unfiltered feedback from the world, telling you where you actually stand. As long as you keep your spirit up and your ego in check, each mistake is just a stepping stone. This is why we bow to our training partners – we acknowledge that we grow together, often by “failing” together. Little by little, hit by hit, the fear of failure loosens its grip. What replaces it is a kind of quiet confidence and humility: confidence because you’ve survived mistakes and improved, humility because you know there are always more lessons ahead.
“Hai, Play!”
At the heart of Hatsumi Sensei’s teaching is an invitation to play. He often ended a demonstration not with a stern command, but with a cheerful “Hai, play!” – essentially, “Ok, go play with it.” At first, I found this puzzling. We were here to learn deadly serious techniques, and he wanted us to play? But watching him, I slowly understood. In play, we become fully present and spontaneous. We drop our pretenses and explore. And that is exactly the state you need for true mastery.
Hatsumi Sensei once explained his teaching philosophy to a journalist, saying that he doesn’t spoon-feed students technique. “Here I do not teach,” he said, meaning he does not lecture or force understanding. Instead, he demonstrates how he moves and then encourages everyone to incorporate that movement themselves. This approach requires the students to be present and creative – to find the lesson through their own bodies. Of course, we have kata (forms) as the foundation, the structured techniques that we drill. But, as he noted, “no matter how skillful you may become at kata, by themselves they are not enough.” The real art emerges when you let go of kata and play freely with the principles. That’s why after showing a form, he would say “Hai, play!” rather than “Do it exactly like this.” It was an open invitation. In those moments, the dojo felt less like a class and more like a laboratory or an artist’s studio. We were allowed to be inventive, to find what worked for us, under the gentle guidance of Sensei’s eyes.
I’ve seen tough martial artists from around the world – soldiers, police, hardened individuals – come to the dojo and within minutes be giggling like kids when Hatsumi Sensei pulled a prank or did something unexpected in training. It’s as if he dissolves the macho facades and brings everyone to a state of natural honesty. I’ll never forget the sight of a huge foreign student, after being effortlessly floored by Sensei’s “light touch,” sitting up with a baffled expression – and then bursting into laughter along with everyone watching. The tension in that student (and in all of us observers) broke in an instant. We laughed not because it was funny per se to be thrown, but out of the delight of witnessing something profound and unexpected. Hatsumi Sensei’s art often has this effect – it feels like a magic show where you’re both the audience and the volunteer on stage. Instead of applause, the response is laughter and a brightening of the spirit.
In these moments, important things are happening beneath the surface. The laughter means we’re relaxed, not clenched by fear. The play means we’re experimenting, not trapped in rigid doctrine. And the presence – that intense focus in a joyful atmosphere – means we are completely in the now. This state is sometimes called mushin (no mind), where you’re not overthinking techniques or worrying about outcome. It emerges naturally when you’re having fun and fully engaged. Hatsumi Sensei cultivated this state in us by keeping the training light. It sounds almost paradoxical – treating deadly techniques as a source of joy – but I believe this is one of the grandmaster’s greatest secrets – to be happy, no matter what. Joy opens up the learning receptors in us. A playful mind is an open mind, and an open mind absorbs everything.
Hatsumi Sensei himself embodies this principle of playfulness. Beyond the mat, he is an artist, a musician, a healer – endeavours that require creativity and openness. He often reminded us not to become “martial idiots” who only know violence. The goal was to become well-rounded human beings. There’s a famous phrase in our training hall: Bufu Ikkan, which roughly means “Walk the martial wind consistently (through life).” Hatsumi interprets this as living life fully and artfully through the martial ways. Once, when asked for some profound guidance, he simply said, “There is no way. Live!”. I take that to mean: don’t obsess over finding a single path or secret – just live your life, moment to moment, with awareness, and everything will fall into place. It’s an encouragement to trust in the skills you’ve ingrained and improvise with confidence, getting better over time, whilst still learning to “fail forward”, grinning broadly when floored in the dojo.
In the end, all these subtle teachings – slowing down, creating slack, embracing failure, and playing – weave together into a resilient, adaptive, and joyful approach to martial arts and to life. They form an invisible architecture holding up every technique and every decision I make under pressure. The beauty of it is that you might not notice these beams and pillars at first; a punch looks like just a punch, a throw just a throw. But with time, you start to perceive the open space (kūkan) around the punch, the slack timing in the throw, the little mistakes that were overcome to make it work, and the smile in the heart with which it was given. It’s like entering a dimly lit old dojo: initially you only see the fighting going on, but gradually your eyes adjust and you notice the wooden rafters above, the architecture that’s been there all along supporting the whole experience.
So, as I continue walking this path, I find myself more and more drawn to try and understand the invisible architecture. I try to slow down more, and notice things I used to miss. I give myself and others slack, knowing that freedom and patience bring out the best in us. I don’t fear failure as I once did – I even welcome the insights it brings. And I try to remember, even in serious times, to keep a playful heart. In the dojo of life, a playful heart is young and resilient. In a deep sense, Hatsumi Sensei and the other teachers were showing us that martial arts, at its highest level, is the art of being fully alive. It’s about handling whatever comes – an attack, a setback, a sudden change – with a calm, open, and ready spirit. And the secret scaffolding enabling that ability is built gradually, quietly, through these four principles.
As I finish this reflection, I can almost hear Hatsumi Sensei’s voice ringing out in the distance: “Hai, play!” – and I smile, bow, and carry on, grateful for the invisible architecture that holds me up.
There is no single way.
Just live – and …keep going.
