'When they attack I am already standing behind them'
I'd love to be that good. I'm not. The level of preception and knowledge that is required for this to happen are beyond my abilities as a human being.
In my experiences in dealling with real threats and effective attacks (real threats), I simply cannot do this and it requires me to interupt and change the situation by dealing with the core of the threat.
If I could be behind them before they could attack, then I would not need to ever carry weapons and could go into combat empty handed. A nice thing to be able to do.