Aikido training usually begins by practicing techniques against wrist-grabbing type attacks (tedori). But knowing how to reverse such grabs to control and down your opponent is not aikido, namely because no true budoka ever allows an attacker to simply take hold of his wrist. Rather, he takes the initiative in striking (ate) before his opponent actually arrives with his attack. This is the rhythm, or "breath" (kokyu) of striking.

Shoji Nishio Sensei
Yurusu Budo (pg 56)