We were taught that a dog is helpless once it has a hold of the pre-padded arm offered to it. They are trained to bite the first arm offered to them and in view, not the one behind the guy's back withthe knife.
It is important for them to be holding your arm because they cannot defend themselves (instinct won't let them let go anyway) and they will not yelp either. It's the same as sneaking up behind a sentry and gagging him with your hand before dispatching him.
Dogs sense fear and if you're not affraid of them, then they are fearful. I've outstared dogs before now. Shouting at dogs and making the first move scares the sh*t out of yappy and barking dogs.
I had a friend who once owned a Alsation bitch guard dog who the first time I visited hammered down the drive and stood there barking at me. I yelled at it to sit down, and it did but kept on barking at me. So I told it to shut up as well, which it did. It hid behind my friend when came out the house.
It was terrified of me afterwards and would hammer down the drive, realise that it was me walking up it and hide under a garden shed.
This same guard dog once chased a thief over 2 miles and came back with his trouser leg, so it wasn't a softy. To the dog, I was the Devil incarnate though.
Knowing dog psychology was something else the Army taught me as part of my role back then.
Guard dogs are invaribly bitches as males dogs are more likely to run away, where as bitches have the instinct to defend.
Rottweilers are soppy things as pets but eat food like a Hummer eats gasoline. They also like to be the centre of attention. They were bred as a wardog in ancient times.