Underhook Half Guard (Bottom)

What This Is

Underhook half guard is the offensive configuration of half guard bottom. The bottom player has one arm inserted under the top player’s armpit — on the same side as the trapped leg — with the shoulder pressing into the top player’s chest and the hand reaching behind the top player’s back. The bottom player is on their side, not flat on their back. The hip that corresponds to the underhook side is off the mat. The leg trap is in place.

The critical distinction is between underhook half guard and crossface half guard. These are not two equally valid positions — they are the offensive and defensive positions of the same configuration, respectively. When the bottom player has the underhook, they control the near hip and the near shoulder of the top player. The top player cannot flatten the bottom player easily; they cannot advance without first dealing with the underhook. When the top player has the underhook (the crossface), the situation is reversed: the top player controls the bottom player’s near shoulder, the bottom player is being pressed flat, and the pass is very close to complete. Underhook half guard is not half guard — it is winning half guard. Crossface half guard is losing half guard.

The underhook is the foundation of the entire half guard bottom offensive system. The dogfight stand-up requires it (standing without the underhook is standing into the top player’s front headlock). The lockdown works best with it. The underhook sweep requires it directly. The back take from half guard begins with it. Practitioners who understand that half guard is fundamentally an underhook battle — and who prioritise getting and keeping the underhook above all other concerns — will find that the specific sweeps and exits become almost secondary. The underhook is the enabling condition. Everything else follows from it.

The Invariable in Action

The underhook is INV-G03 made concrete in the half guard context. Getting the arm under the top player’s armpit is establishing a connection to the inside of the top player’s near elbow — to the inside of the near arm — that controls the near shoulder and, through it, the near hip. This connection does two things simultaneously: it prevents the top player from driving their weight into the bottom player’s chest (which would flatten them), and it gives the bottom player a directional handle to redirect the top player’s momentum. When the bottom player has the underhook and is on their side, they are not defending against the pass — they are threatening the sweep and the back take. The underhook is the difference between a guard that is being passed and a guard that is attacking.

The underhook and hip mobility are interdependent in half guard. The underhook prevents the top player from flattening the bottom player because it controls the near shoulder and prevents the top player from driving weight directly down. A bottom player with the underhook can turn their hip off the mat and maintain mobility because the underhook gives them the shoulder control to create that space. Conversely, a bottom player who is flat — who has lost hip mobility — cannot get the underhook because the top player’s weight is already pinning them. The underhook must be fought for before being flattened, not after. Once the hips are flat, the leverage needed to insert the underhook is gone. This is why half guard instruction at every level begins with “get to the side” — the side position is the precondition for the underhook fight.

Underhook half guard is, structurally, a hip height competition. The top player’s goal is to keep the bottom player flat — hips pinned, shoulder down. The bottom player’s goal is to get the hip off the mat and the underhook shoulder above the top player’s near shoulder. When the bottom player achieves that elevation, the leverage relationship inverts: the bottom player now has a directional handle pointing upward and forward, while the top player’s weight is now working against a rising structure rather than a flat one. The underhook sweep and the dogfight stand-up are both expressions of this height gain — they are the consequences of successfully achieving higher position.

The underhook in half guard is an invitation for the top player to react. Each reaction opens a specific attack. When the top player drives their weight down to resist the underhook drive, the sweep’s hip leverage becomes available — their downward force feeds the forward rotation. When the top player turns away to block the back take, the seatbelt reach becomes available. When the top player bases wide to prevent either attack, the dogfight stand-up opens. The practitioner who understands this plans for the reaction before driving the underhook — the specific sweep or back take is selected in advance based on the top player’s most likely response.

Entering This Position

Fighting for the Underhook from Flat Half Guard

The most common scenario: the bottom player is in half guard but has not yet secured the underhook. They are on their back or partway to their side, and the top player is fighting to crossface or is already applying the crossface. To get the underhook from here, the bottom player must first get to their side — hip escape toward the trapped leg side, come up on the elbow. From the side position, the near arm is inserted under the top player’s armpit. The insertion is not a slow reach — it is a drive. The bottom player drives the near shoulder into the top player’s chest and pumps the arm up and under, aiming to get the hand behind the top player’s back. Once the hand is behind the back, the underhook is established.

Underpumping Against the Crossface

When the top player already has the crossface and is pressing the bottom player’s near shoulder down, the bottom player can “underpump” to retrieve the underhook. From flat, the bottom player bends the near arm elbow tight to the body, points the near hand toward the top player’s hip, and pumps the arm under the top player’s crossfacing arm — driving under it rather than trying to push it off from above. The underpump is a motion that goes down and under the top player’s arm, not up and against it. Once the near arm is under the top player’s crossfacing arm and heading toward the armpit, the underpump is converting into the underhook. The bottom player simultaneously hip escapes to the side to complete the transition.

Creating Space with the Knee Shield

When the top player’s weight is too heavy to underpump directly, the bottom player can first create space using the knee as a frame. The free leg’s knee is inserted between the bottom player’s body and the top player’s hip, creating a brief moment of distance. In that moment of distance, the bottom player hip escapes and drives the underhook in. The knee frame is a temporary tool — it creates the space, and the underhook follows immediately into that space. Using the knee frame without immediately following with the underhook only delays being flattened; it does not prevent it.

Entering from Seated Guard — Taking the Underhook from the Start

When the bottom player in seated guard chooses to enter half guard — pulling the top player’s knee in to establish the trap — they can fight for the underhook before the top player settles. This is the cleanest entry: the top player is still establishing their position, their weight is not yet settled, and the underhook can be won before the crossface battle even begins. This requires the bottom player to be proactive — recognising the half guard entry and going for the underhook simultaneously with the leg trap, not after.

From This Position

With the underhook established and the hip mobile, the bottom player has multiple offensive options. The top player’s awareness of these options is what makes each individual option work — defending one opens another.

Dogfight Stand-Up

The most direct use of the underhook. With the underhook under the top player’s armpit, the bottom player posts the near foot and drives their hip up, coming to the near knee and arriving in the dogfight configuration. The underhook protects the bottom player’s head during the stand-up (the top player cannot easily shoot the front headlock because the underhook controls their shoulder) and gives the bottom player the connection needed to take the back once in the dogfight. See the Dogfight page.

Underhook Sweep

From the underhook position on the side, the bottom player drives forward — hip and shoulder simultaneously — and attempts to roll the top player over the trapped leg. The top player’s weight is being redirected: the underhook lifts the near shoulder while the hip drive turns the top player over the near side. This is a direct sweep that requires the bottom player to be on their side with mobile hips (not flat) and to drive with both the hips and the underhook arm simultaneously. A sweep driven only by the arm will stall against a heavier top player; the hip drive is what generates the force.

Add the Lockdown

With the underhook in place, the bottom player can add the lockdown (the figure-four calf hook on the trapped leg) to strengthen the half guard control and add the electric chair and hip whip sweep to the option set. The combination of underhook plus lockdown is very strong: the underhook controls the top player’s upper structure while the lockdown disrupts the lower structure. See the Lockdown page.

Back Take

When the top player turns to defend the sweep — rotating away from the sweep threat — the bottom player’s underhook hand can reach around the top player’s waist and establish the seatbelt directly. The underhook is already under the armpit; extending it to the seatbelt is a matter of reaching the far hand across the top player’s chest. The top player’s rotation away from the sweep threat creates the angle that makes this work.

Deep Half Entry

When the top player drives hard into the bottom player despite the underhook — heavy pressure from a strong passer — the bottom player can duck under the top player’s body into deep half. The underhook guides the duck: the bottom player’s underhook arm controls where the top player’s body goes as the bottom player slides under. See the Deep Half Guard page.

Common Errors — and Why They Fail

Error: Losing the underhook to the crossface without immediately contesting it. Why it fails: INV-G03. Once the top player wins the underhook battle and has the crossface, the bottom player’s connections are compromised. The top player can now flatten, advance, and pass without the bottom player having a meaningful directional handle to resist with. Each moment spent in the crossface without contesting it allows the top player to advance further. Correction: The moment the underhook is lost, the bottom player has two immediate responses: underpump to retrieve it, or frame the near elbow and hip escape away to create space. Either is better than lying in the crossface and waiting. Passivity in the crossface is the pass completing itself.

Error: Lying flat instead of turning to the hip. Why it fails: INV-G05. From flat, the underhook loses half its value. The underhook controls the near shoulder, but from flat, the bottom player cannot convert that shoulder control into a sweep or a stand-up — there is no hip drive available to combine with the shoulder control. The underhook on a flat bottom player is like a lever with no fulcrum: the connection exists but cannot produce movement. Correction: Turn to the hip before or simultaneously with fighting for the underhook. The side position is not the result of getting the underhook — it is the prerequisite for making the underhook useful.

Error: Keeping the underhook arm passive — resting it under the armpit without driving. Why it fails: INV-G03. A passive underhook is a connection that does not produce control. The arm is under the armpit, but if it is not driving the shoulder and keeping the top player’s shoulder elevated, the top player can still apply weight and flatten the bottom player despite the underhook. The underhook must be active: the shoulder drives into the top player’s chest, the hand grips behind the back, and the arm is actively keeping the top player’s shoulder up. Correction: The underhook is a driving position, not a resting position. If the top player’s weight is still flattening the bottom player despite the underhook, increase the shoulder drive — drive the near shoulder deeper into the top player’s chest. The underhook that drives is the underhook that works.

Error: Attempting the dogfight stand-up without the underhook secured. Why it fails: Standing up into the dogfight without the underhook is standing directly into the top player’s front headlock. The top player’s arm that was crossfacing becomes a front headlock as the bottom player’s head comes up within reach. From the front headlock, the top player has guillotine and neck crank entries and a strong positional advantage. Correction: Secure the underhook before standing. The underhook is the stand-up protection: it controls the near shoulder and prevents the front headlock from being established during the movement.

Drilling Notes

Ecological Approach

Underhook battle game: Both players start in half guard (top player in passing position, bottom player has the leg trap). The top player tries to secure the crossface and complete the pass; the bottom player tries to secure the underhook and sweep, take the back, or achieve the dogfight. Neither player can submit. Run ninety seconds, switch. This game makes the underhook battle the central contest and forces both players to develop real-time underhook fighting skills rather than learning the position as a sequence of cooperative techniques.

Systematic Approach

Phase 1 — Hip escape to side. From flat half guard (no underhook yet), the bottom player drills the hip escape to the side position. Top player applies light pressure. Focus: hip comes off the mat, near elbow is the base, the movement is driven by the hip — not by the arms pulling. Twenty repetitions. (INV-G05 checkpoint: are the hips off the mat at the end?)

Phase 2 — Underhook insertion. From the side position, the bottom player drills driving the near arm under the top player’s armpit. Top player provides moderate resistance to the insertion. Focus: shoulder drive first, then arm pumps under. The insertion is not a reach — it is a drive. Twenty repetitions.

Phase 3 — Underpump from crossface. Top player establishes the crossface. Bottom player drills the underpump — the underhook retrieval from a losing position. Focus: arm goes down and under, not up and against. Simultaneously hip escape to the side. This is the single most important recovery skill in half guard. Twenty repetitions.

Phase 4 — Underhook battle game (ecological), as above.

Ability Level Guidance

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