Ikkyo (First Teaching), also known as Ude-Osae (Arm Securing/Pinning), and some of its variations may also be found in other Japanese fighting arts such as Judo (“Way of flexibility”), Jujutsu (“Combative art of flexibility”), and Aiki-jujutsu (“Combative art of divine harmony”) as well as other Asian and Western hand-to-hand fighting forms.
lkkyo is a cornerstone of Aikido (another of the “pillars”) and represents one of the foundations of the various movement patterns and philosophies. Saotome Sensei describes ikkyo as “the first chapter, and the last” he further states that with lkkyo comes “the application of principle and its philosophical result”.
In each situation the degree and direction of force is different, your position is not always the same, body shape and muscular structure differ from partner to partner, perception and timing change. The application must change accordingly. Technique is, in one second, the creation of form. It is never the same second, never the same form, the same second, never the same form. But the basic principles are always the same .
From a personal point of view, the aspect of ikkyo that appeals to me is that, executed correctly, you can control your partner with little or no pain, effectively giving you and ethical choice (as opposed to nikkyo for example, which, if it has to be applied, hurts like hell whatever!). This ethical decision-making process for me is one of the things that sets Aikido apart.