I think that's where I get lost too like a sumi otosh(sp?) ura. If I breath in during the tenkan motion, then out during the cutting of the hand, what's left for when I step behind to actually drop them?
Some have quoted, "breathing is natural..." I would have to politely disagree, completely when it comes to martial arts.
If that were the case, then everyone would be a master. An example of the just do it and you will learn it properly fallacy is the way that we learn to walk as a toddler. In that case, walking is really "learned controlled falling" and is not very efficient. More walking doesn't improve our understanding of this basic action and takes its toll on the body over time. The truth is, as with walking, most of us breathe very poorly and inefficiently as part of our day-in, day-out unconsciousness. Both walking and breathing as related to martial arts needs to be completely relearned, unlearned actually. That is very difficult and lengthy process, indeed. This is especially true if one thinks that they will somehow stumble upon the correct way over time, just breathing or walking naturally. Again, if this were the case, everyone would be a master.
Learning to breathe (and walk) starts with:
- admitting that there is a problem with one's current method
- imagining that there is another way - a better way, in fact
- believing that someone out there knows this way
- seeking out such a person to learn it from them.
- practice, practice and (yep, you guessed it...) more practice
Techniques are to be executed at the pause, or resting point between the inhalation and exhalation points. This is also the way of breathing during ukemi, as we are to leave no openings in the breath, or mind as we would be susceptible to attack during or just after taking the fall. Technically speaking, the breath, itself, is to be locked before the initialization of Uke's attack. Locking of the breath occurs at the moment when one is neither breathing in or out. This takes substantial practice to understand, and even longer to be able to do during controlled physical activity. To be able to accomplish it when being attacked is even more difficult and should be paramount in one's personal training goals within a martial context. As an aside, the breath is completely effected by the blood and physical constitution and Yin/Yang and Acid/Alkaline balance of one's body. This is why diet becomes so intimately tied to this discussion. This is why O-Sensei's diet, especially that in his later years needs to be more closely observed. Of course, all of this is both studied and practiced as part of O-Sensei's Misogi. This is why O-Sensei's Misogi-no-Gyo needs to be properly learned and practiced in order to understand O-Sensei's Aikido.
I hope that helps.