Re: Regrading grabs in Aikido...
The emptyhand methods that lead to the development of aikido came from problems that had to be dealt with during armed confrontations. It's an art that came from the practices and methods of armed men, samurai.
If you're empty handed it would be foolish of you to try to defeat an armed attacker unless you have no other choice. The first choice is to arm yourself. Being armed is the best thing because when you really want to assault someone you'd want to do it with as much unfair advantage as possible.
The problem with aikido is most practitioners don't understand or have never trained with the armed methods of fighting to have realistic understanding of why aikido methods are the way they are.
It is a weapon based empty handed martial arts system that cannot be fully understood unless the practitioner has a true comprehension of weapon fighting.
Grabs in aikido are a matter of weapon retention and or how to prevent another from using their weapon.
Why would anyone grab someone's wrist from the back...clearly if you want to put someone down the best way is to just whack them on the head when they're not looking.
Killing somone is a no, no then and it's no, no now. How do you subdue someone who probably has a knife or two? You prevent them from being able to access their weapon.
Knowing that people will prevent you from accessing your weapon and that you also need to to prevent people from accessing their weapon a method must be developed to solve this problem.
Knowing that in a real fight there would probably be more than one person trying to keep you from getting to your weapon you must also figure out a way to minimize the time spent with each opponent.
In "serious" fight, meaning life or death, you need to access your weapon as soon as possible. If it turns serious enough where your opponents goal turns from subduing you into killing you because you're resisting and pose an imminent threat you also need to figure out a way disarm them or at least get in a range where you can prevent them from accessing their weapon while keeping yours.
If they were able to access their weapon you need to be able to bridge the gap between no contact and contact range without getting hit.
This means you've got to get close enough to grab them and the whole process goes on...