Sashi-Ai 差合

Sashi-ai 差合 is a classical budō and kenjutsu term that generally means mutual thrusting or simultaneous attacking. In kenjutsu, it describes a situation where both swordsmen initiate a thrust or cut at the same moment, resulting in: a crossing of blades; a double-attack scenario; a mutual-entry; a contest of timing and spirit (kiai). It often appears in descriptions of kata where the timing is very tight.

Sashi-ai can describe a high-level exchange where both practitioners enter simultaneously and attempt to dominate the center line. This contest of initiative and timing is common in: Itto-ryu timing concepts; Katori Shinto-ryu paired kata; Yagyu Shinkage-ryu mutual initiative drills; classical spear (yari) kata; and some jō kata where both sides thrust at the same instant.

Sashi-Ai vs Ai-Uchi

Sashi-ai (差し合い) and ai-uchi (相打ち / 相撃ち) are not the same thing even though both involve simultaneous actions.

Ai-uchi 相打ち / 相撃ち means mutual striking or striking each other, often in a situation where both combatants strike and both are hit, often fatally. In koryū kenjutsu, it is considered a failure of strategy. The ideal is always to survive while cutting the opponent. Many densho explicitly warn against ai-uchi as a last resort or a dishonorable exchange. Some ryuha teach how to avoid ai-uchi at all costs.

In kendo, ai-uchi means to both attack simultaneously and both “score” at the same instant (usually no point is awarded; it is considered neutral). It’s a double kill or a mutual hit. Both lose.

Sashi-ai (差し合い / 差合) refers to a situation where both sides extend, thrust, or enter at the same moment, but the outcome is not yet determined. Sashi-ai is not necessarily lethal — it describes the engagement, not the consequence. Conceptually, one will win the exchange. This term appears more in koryū paired kata and spear work.

So, with ai-uchi, both cut each other (double-kill). The outcome is decisive and negative. In sashi-ai, both enter simultaneously. The outcome is undetermined, tactical, and part of kata timing.

Concept AI-UCHI (相打ち) SASHI-AI (差し合い)
Literal meaning mutual striking mutual entering/extending
Action both strike, both land both initiate attack at same moment
Outcome both die / both score outcome depends on timing and skill
Judged as mistake or undesirable advanced timing scenario
Found in kenjutsu, kendo koryū kenjutsu, yari, jōdō
Spirit desperation, failure sen (initiative) contest

 

Relationship to “Sen” (Initiative Timing)

Ai-uchi occurs when neither controls timing. It is “no-sen,” a failure of initiative. Sashi-ai occurs within sen-no-sen or go-no-sen: one may seize initiative at the exact moment of mutual entry; one cuts into the opponent’s attack; one dominates center while both extend. It is a training scenario, not a fatal result.

Translation

sasu/sato insert, to thrust in, to present, to extend (the arm), to offer
aito meet, to come together, to match / harmonize, to engage
差合sashi-aimutual insertion / mutual engagement / exchanging attacks / two people thrusting/engaging at the same time.

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