True, have two border collies,they stay on alert 24/7. Let me know when anyone comes around they don't know.

A pit sometime ago, picked a fight with one of them and attacked him the other one jumped on him and the one attacked

Got free from the pit and both of them kicked the shit out of the pit. Felt bad for him but he started it.

Border collies are not mean,and smartest of all the dogs.

When you get a dog, get two, have a pound pup also and he is not as smart but he has heart and can be sound off when he does not know who knocks on the door.

They work as pack.
Couple of medium size 60 or 70 pounds pups be you best bet.

Have a friend who trains mean ass guard, German Sheppard's and he is always worried about them attacking someone.