A spearman drives his point dead-center at your chest. That is one way to send your power at a man. A second man lets your charge come, pivots on his hip, and your own momentum throws you spinning past him into the dirt — he barely touched you. That is a second way. A third man you never even fight: you walk into the room, feel something settle and tighten in the air around him, and somehow the fight you came to start no longer seems like a good idea. That is the third way, and it is the strangest of the three.
The old masters of bujutsu noticed these were not random styles. They were three directions. You can send coordinated power straight at a target, you can send it around a target, or you can let it radiate out in every direction at once until it owns the whole space. Linear, circular, diffusive. The book says the debate between these three "has influenced the martial arts of yesterday and continues to affect their modern derivations."1 Get this scheme into your hands and most of what looks like a hundred different fighting styles resolves into three answers to one question: which way does the energy go.
This is the unifying grammar of how projected power moves — the three-fold scheme of ki extension that sits underneath the specialized arts, the spear and the sword and the empty hand and the aikido throw, and tells you what they have in common. The vault already holds the hara and ki life-force doctrine (the energy itself, where it lives, how it is centralized) and the kiai/zanshin cluster (the shout and the lingering awareness). This page is none of those. Its lane is narrower and stranger: not what the energy is, but the three directions it can be sent — and the fact that an art's entire character follows from which direction it chose.
Here is the mechanism that makes this genuinely cross-domain. The three modes require both the outer technique-geometry of bodily movement AND the inner theory of ki/energy-projection simultaneously — each mode is at once a way of moving the body and a way of directing consciousness, and neither the biomechanics nor the energetic theory explains the three-fold scheme alone. Watch what happens if you try. Drop the energetic half and you have three footwork patterns: stepping forward, turning aside, standing still. That tells you nothing about why the third one — standing still and radiating — could end a fight before it began. Drop the biomechanical half and you have three vague metaphors about mind. That tells you nothing about why linear extension "goes through" and kills while circular extension "goes by" and merely diverts.2 The scheme only exists where the body's line and the mind's direction are the same line. Irimi is not a step plus a separate intention; it is one act that is both. The three modes are three ways the moving body and the directed mind fuse — and you cannot describe even one of them in a single domain.
Start from the thing all three share. Long before you pick a direction, the masters wanted the bujin to fuse his inner powers — perception, awareness, will — with his outer powers of execution, so that mind and body acted "like two wheels of a cart."3 That fusion is the engine. The three modes are three ways to point it.
Linear. Power extended in a straight line from its source to its objective, the target hit frontally, perpendicularly. The book names it omote and irimi — entering.4 The spear's thrust, the sword's frontal cut, the karate punch, the sumo charge, the judo entering throw: all the same answer. And linear extension has a signature effect. It "goes through" the target. It alters his structure. Linear ki can kill.
Circular. Power extended in a curve from its source, the target hit tangentially, ura and tenkan — turning.5 You do not meet the force; you let it arrive and you redirect it, sending the man "whirling orbitally away" by his own momentum. And circular extension has the opposite signature. It does not go through; it "goes by." It removes the man from his position of power without altering his structure. Circular ki stuns and diverts. It need not injure at all.
That contrast is the whole strategic debate of the martial arts compressed into a sentence: do you destroy the structure or do you displace it. Penetrate or redirect. Kill or unbalance. The book is careful, though — the line between the two blurs in practice, because a man can begin circular, evade the attack, and end with a perpendicular strike turned back on the opponent. Was that circular or linear? By its effect on the target, linear. True circular extension is circular "from beginning to end, not only at the beginning."6 The direction is not a label you slap on at the start; it is the shape of the entire act through to its effect.
Diffusive. The third mode breaks the pattern, and the book treats it almost reverently. Power extended not in a line and not in a curve but outward in all directions at once — "diffusive and irradiating — permeating the entire environment and often controlling it psychologically even before combat developed, to the extent of actually changing the conditions for its occurrence."7 This is not a technique you do to an opponent. It is a field you generate that reshapes whether there is an opponent at all. And the book is blunt about its strangeness: this was "the type of mental control exercised by the man of peace, the sage, the mystic" — something the bujin could admire from afar but rarely imitate, because the moment he truly achieved it "he ceased to be a bujin."8 The third mode is the door out of combat. The first two win fights; the third dissolves them.
That asymmetry is the internal logic. Linear and circular became "the two main cornerstones of instruction" — the working tools, the things you drill.9 Diffusive sits above and outside them, the rare ceiling almost no fighter reached, because reaching it meant becoming something other than a fighter.
This page hands the vault a direction-grammar for projected force — a way to read any act of influence by asking which of three shapes it takes. Straight at the target (penetrate, alter, destroy). Around the target (redirect, displace, unbalance using the target's own force). Or radiated everywhere (saturate the field until the contest's terms change before it starts). That triad is portable far past swords.
It also hands the vault a ceiling that exits the game. Two of the three modes are how you win; the third is how you stop needing to. Anywhere a discipline has a tier of mastery that doesn't beat the opponent but removes the conflict — the negotiator nobody wants to cross, the presence that ends the argument before it forms — you are looking at diffusive extension, and this page gives it a name and a place in a system.
Watch what happens when an art bets its whole identity on one of the three directions. Aikido is the clean specimen, because its name is the choice: ai-ki, the harmonizing of energy, and its signature movement is tenkan, the turn.10 Aikido chose circular and built everything on it.
See the consequences cascade. Because aikido extends power around rather than through, it "goes by" rather than "goes through" — and that single geometric fact produces the entire ethic the art is famous for. The man is not destroyed; he is sent "whirling orbitally away" and lands, structure intact, position lost.11 The much-advertised non-violence of aikido is not first a moral stance bolted on top of a fighting method. It is the strategic signature of circular extension showing up as ethics. Choose the curve and you get displacement-without-injury for free; the philosophy of harmony is the curve, described in moral language.
Now see what it cost. By leaning so hard on circular, aikido largely surrendered the linear mode — the frontal penetration that "goes through," that kills. Critics who call the art combatively soft are, in this frame, simply noting that it declined one of the three directions on purpose. That is not a flaw in aikido; it is the price of its coherence. You cannot specialize in the turn and also keep the thrust as your center of gravity. The art's strength and its limit are the same decision viewed twice.
And here is the part that makes aikido the perfect case. It reaches for the third mode openly. Aikido's founder framed the art as a path of reconciliation, of resolving conflict rather than winning it — which is precisely the diffusive ambition, the attempt to control "the conditions for combat's occurrence" so that no real fight is needed.12 So aikido is a single art trying to live in two of the three modes at once: circular as its working technique, diffusive as its aspiration — and almost wholly refusing the first. Read through the three-mode scheme, aikido stops being a mysterious soft style and becomes a precise, legible bet: we will win by turning, and we will aim past winning entirely.
You stand across from a partner. Before you move, decide nothing with words — feel the question in your hips: through, around, or everywhere.
You try the first answer. He comes; you step straight in, irimi, your whole center driving on one line from your belly to his. You feel it: there is no give in this, no mercy in the geometry. The power wants to pass through the space he occupies, and if he does not move he is simply where your line is. You notice your breath drops, your shout wants to come, everything narrows to the single axis. This is linear, and you feel why the book says it "goes through" — your intention has no room in it for the man to remain standing.
You reset and try the second. He comes again; this time you do not meet the line. You let his force arrive and you turn, tenkan, pivoting on your hip so his momentum keeps going where you redirect it. You feel the difference in your body immediately — there is no collision, almost no effort, and the harder he committed the further he flies. You are not destroying his structure; you are stealing his position and handing his own force back to him curved. You notice you could have done this without hurting him at all. That softness is not your kindness. It is the shape of the curve.
Then you stop moving entirely and try the third, knowing you will probably fail at it, because almost everyone does. You settle your weight, you let your awareness spread out past your partner to fill the whole room, and you try to extend outward in every direction — not at him, but everywhere, until the space itself feels occupied. On the rare day it works you will feel him hesitate before any technique, the readiness draining out of the encounter. Most days you will feel nothing and step back into the turn. That is honest. The third mode is the ceiling, and the moment you truly reach it you will notice you no longer want to fight him — which the old masters said was exactly the point, and exactly the moment you stop being a fighter.
You can name which mode an art or a person runs by its tells.
Linear is at work when force meets force head-on, when the aim is to penetrate and alter — to break the opponent's structure, not just move it. The signature is the perpendicular line and the through-effect: the man is changed where he stands. The diagnostic question is simply did the power pass through him? If his structure is broken, it was linear, whatever it looked like at the start.
Circular is at work when the practitioner refuses the collision, when the opponent's own committed force is the engine of his undoing, when the man ends displaced but intact — "stunned or diverted," sent orbiting away from his position of strength without lasting injury. The tell is effort that drops as the opponent's commitment rises. The harder he came, the easier it was. That inverse relationship is circular's fingerprint.
Diffusive is at work when nothing visible happens and the contest changes anyway — when a presence settles a room, when the fight does not start, when the conditions for conflict quietly dissolve before the first move. It is the hardest to see precisely because its success looks like nothing happening. The diagnostic: ask whether the win required a technique at all. If the conflict was neutralized before it formed, you witnessed the third mode — and you should be appropriately suspicious, because almost no one actually has it, and many who claim it have only stillness without the field.
The factual spine is one passage in Ratti and Westbrook, a popular synthesis drawing on early-twentieth-century authorities (Harrison, Durckheim, Suzuki) and on the Chinese inner/outer-energy (nei chia / wai chia) tradition it explicitly names as the scheme's ancestor.13 The three-fold linear/circular/diffusive structure is the book's own organizing claim, and it presents it as a real historical "trend" within bujutsu doctrine rather than a tidy modern invention. Treat the triad as a useful map with high confidence; treat the energetic metaphysics underneath it — ki as a literal projectable force — with the book's own caution, since it repeatedly flags that genuine ki use was "comparatively limited," wrapped in words like esoteric and mysterious, and possibly indistinguishable from "sheer illusion projected by certain peculiarly endowed personalities."14
The live tension the source plants and does not resolve: is the third mode a real higher capacity, or a romantic frame for ordinary intimidation and reputation? The book locates it with sages and mystics and calls it the door out of combat — but it also admits the bujin could almost never reach it. So the open question is sharp: is diffusive extension a distinct mode of projected power, or is it just what we call linear and circular power after a man has become so dangerous that no one tests him? The scheme needs the third mode to be more than fearsome reputation, and the source never quite proves that it is.
The interesting friction is not between authors but inside the practitioner's own body, and Ratti and Westbrook stage it honestly. Train the linear mode and your nervous system learns one truth: commit fully on one line, there is no half-measure, the first exchange may be the only one, and mercy is geometrically unavailable. Train the circular mode and your body learns a contradictory truth: never collide, let the other man's force be the weapon, the harder he tries the less you do. These two trainings do not blend into a comfortable average. They feel opposite. The book records that masters argued the linear-versus-circular question so fiercely that "its echoes are still reverberating today," and you can feel why — a body deeply grooved into entering resists turning, and a body grooved into turning has unlearned the killing line.15
Where they converge is underneath, in the shared hara fusion both demand — and the rare practitioner who can hold both is described almost as a different order of being, the one for whom an initially circular evasion can resolve into a perpendicular killing line without a seam.16 That seamlessness is the real mastery the source points at, and it is experiential, not doctrinal: not knowing both modes as facts but having a body that can flip between through and around inside a single movement, choosing the target's fate — destroyed or merely displaced — in the instant. The third mode then hangs above both as a still stranger convergence: the place where you have so fully integrated the first two that you no longer need either, and the conflict ends before it starts.
Plain version of why this scheme reaches across the vault: it is a grammar of which direction force goes, and direction-of-force is a question every combative and persuasive art has to answer, whether it knows it or not. Three modes — through, around, everywhere — and an art's entire character falls out of its choice.
Cross-domain: Maai — Combative Distance System — maai is the grammar of combative distance; this page is the grammar of combative direction. Set them together and you get a near-complete coordinate system for projected force: the interval tells you when and how far, the three modes tell you which way. They are not the same axis and that is exactly why they need each other. Linear extension wants a specific distance — the spear's wall, the perpendicular collision — and collapses if the interval is wrong. Circular extension wants the opponent inside the distance, committed and overcommitted, so his momentum can be turned. Diffusive extension explodes the whole concept of an interval, because a field that fills the room has no single distance at all. The insight neither page produces alone: distance and direction are coupled — choosing a mode is partly choosing a distance, and a master's real skill is not picking one or the other but holding the pair, manufacturing the interval that makes his chosen direction lethal. The turn only works at the range where the thrust would have, one beat later.
Cross-domain: Kiai and Zanshin — The Spirit Cluster — that page holds the shout that concentrates power to a point and the lingering, all-around awareness that surrounds the encounter. Lay the three modes over it and the cluster organizes itself by direction. The kiai — the focused vocal projection of ki along the strike — is linear extension made audible: power fired on one line at one target, "the vocal vector of transmission of power from its abdominal source to its target."17 Zanshin — the continued, omnidirectional awareness that does not collapse after the technique — is diffusive extension's smaller cousin, a field of attention thrown out in all directions rather than a thrust sent on one. The insight the pairing produces: the spirit cluster is not two unrelated practices but two of the three directions of one energy — the point and the field — and the third practice, the turn, the circular redirection, is the one the cluster is missing, which is precisely what this page supplies. Read across, kiai/zanshin and the three modes complete each other: the cluster names the point and the field; the three-mode scheme adds the curve between them and reveals all three as the same ki aimed three ways.
History: Aikijutsu and the Daito-ryu Lineage — that page traces the lineage from which aikido descended, the aiki arts of harmonizing and turning. The three-mode scheme explains what that lineage technically committed to: it is the historical home of circular extension as a complete system, the tradition that bet on the turn over the thrust and passed that bet down to aikido. The insight: a "lineage" in the martial sense is partly the transmission of a directional choice — Daito-ryu and its heirs carried the circular answer through generations the way the spear schools carried the linear one, and the family resemblance across an aiki lineage is at bottom a shared answer to the through-or-around question. Tracing the lineage and tracing the mode turn out to be the same act seen from two sides.
The Sharpest Implication There are not a hundred ways to project power; there are three, and everything else is detail. Straight through, around, or everywhere — penetrate, redirect, or saturate — and an art's entire personality, even its ethics, falls out of which direction it chose. Aikido's gentleness is just the curve described in moral words; the spear's lethality is just the line. Take that seriously and it stops being about swords. Every contest of influence — an argument, a negotiation, a market move, a confrontation — is also a choice of direction. You can meet the other force head-on and try to break it (linear, and you had better be the stronger structure). You can let it commit and turn it against itself (circular, and the harder they push the better it works). Or you can become the kind of presence that changes the conditions so the contest never quite forms (diffusive, the rare ceiling almost no one reaches). Most people only own one of these and call it their personality. The master owns the choice.
Generative Questions