I have a Geant Schnauzer.
He is 20 months old and doesn't bark to alarm us when I have guests or intruders if I may put it this way.
His parents were very wild and ferocious this is the reason why I bought him but he would only bark if he is angry with me (for example he wants me to release him off the kernel) if not he does't bark at all.
He has been on training for more than a year now.
He masters the obedience stage but I haven't seen other aspect of his training like attack, barking and the like.
These dogs are not usually aggressive. If you want a more aggressive dog why don't you look into rotties or chows. vetcare