Luis, a former uchi-deshi (live-in student), taught last night's class. Hailing from Spain, he's a warm-hearted, friendly guy who loves to plant guys like me into the ground! All kidding aside, it was great when he lived in the dojo and I miss seeing him every day.
The class focused on yokomenuchi, which is a kind of aikido stylized attack. It's a strike to the side of the head with the hand blade. The real-world approximation may be a hook punch, but not a jab.
All attacks in aikido have to be committed. Despite aikido's moniker as "the Art of Peace," it's not a fighting art, but a real warrior art, meaning the contests are supposed to be for life and death.
There are several different ways of dealing with yokomenuchi, so we further focused on an irimi opening. Irimi is an entering move, going into your opponent's space during his attack. This seemingly paradoxical idea gets its justification from the fact that an attack has a zone of effectiveness. Before or after this zone, the attack is weak and can be more easily directed. So if the strike is intercepted (not blocked) before it reaches its full speed and power, it can be the beginning of an effective aikido technique.
As usual in Luis' classes, we explored many variants and I saw a few things I'd never seen before. His idea for yokomenuchi, at least for last night, was a bit different than normal. He had us irimi, but, accompanied with an atemi (distractionary strike), still allowing the yokomenuchi strike to continue, guiding it into the other hand. I am more used to doing this with a different body position (tai subaki), usually moving out of the range of the strike if allowing it to continue.
After the irimi, we would tenkan, and then be in a position to throw or immobilize uke in various ways.
Tenkan is a 180 degree turning move and is a fundamental part of many aikido techniques. One key concept of aikido is to be the "center of the circle" and tenkan allows this in many cases.
Here's a video of Yamada-sensei (our chief instructor) defending against yokomenuchi: