Our recently deceased old girl beagle, had a very deep bark when she wanted to sound fierce, and if someone came to the front door she did not know, you might think there was a huge dog inside. But, if you actually came in she was the sweetest dog. She had the territorial instincts to some extent, but not the temperament to back it up.
The newer beagle, doesn't have much in the way of territorial instincts yet, except where tasty looking rabbits and other small critters are concerned.
Personally, I think unless you want to spend a lot of money on dog training, your best bet is not to rely on a dog for much more than a trip wire. They are pretty good at that, but unless you have expensive professional training for the dog, you are best off not trying for an attack dog. Most dogs have some instinct to warn their humans if someone is sniffing around and shouldn't be, but you really don't want the dog to attack except on command. A dog attack is potentially lethal and needs to be considered in that way, similar to owning firearms.
