From AikiWiki - AikiWeb Aikido Information

[edit] Ai Uchi:　合い打ち

"Mutual kill." An outcome of a duel where each participant kills the other. In classical Japanese swordmanship, practitioners were often encouraged to enter a duel with the goal of achieving at least an AI UCHI. The resolution to win the duel even at the cost of one's own life was thought to aid in cultivating an attitude of single-minded focus on the task of cutting down one's opponent. This single-minded focus is exemplified in aikido in the technique, ikkyo, where one enters into an attacker's range in order to effect the technique.