An ura movement takes nage to uke’s outside flank
to an area we might describe as uke’s “dead zone.”
Many Japanese martial arts use specialized terminology to describe the dynamics of a martial encounter. A common set of terms used are “Go no Sen” (late initiative), “Sen no Sen” (simultaneous initiative or blending) and “Sen Sen no Sen” (initiative before the attack is launched).
In this context, “Go no Sen” is the lowest level scenario where the attacker (I will use “uke” here) initiates the attack, and the defender (here “nage”) responds to this offensive act.
Several things become evident if we analyze the “Go no Sen” scenario. Since uke has launched the attack, his move precedes nage’s defensive response. Thus, uke has a timing and distance advantage. Conversely, nage has a minimized time frame to respond before uke makes contact. Generally speaking, because of these negatives, it is preferable to avoid “Go no Sen” situations as a martial strategy where possible.
Basic to responding in a “Go no Sen” scenario is removing oneself from the line of attack. This might involve escaping from the scene, entering to either flank of uke, or most often in an aikido context, executing an ura or turning movement to evade the attack.
One of the favorite drills in aikido for learning how to turn away from the attack to safety is tai no henko. This is a blending exercise that aikido’s founder Morihei Ueshiba devised and would demonstrate in every class.
You may have never thought of it in these terms, but an ura movement in most instances takes nage to uke’s outside flank to an area we might describe as uke’s “dead zone.” Here uke’s movement and vision are restricted, and he becomes vulnerable to nage’s counter maneuver.
Other tools that can aid in responding to a go no sen attack are atemi (striking) and kiai (combative shout). When used properly these actions can partially or completely neutralize uke’s attack and allow nage to regain the advantage.
An area of concern in aikido as practiced widely is that many aikidoka, beginning and advanced alike, remain on the level of go no sen responses to all attacks. In other words, they develop the habit of responding to uke’s initiative which, from a common sense martial viewpoint, is a poor strategy. The Founder most often demonstrated the higher level martial strategies, especially the “Sen sen no Sen” strategy where nage perceives and preempts uke’s attacking intent. These are learnable skills and serious students should understand and aspire to these higher levels in their training.