you need a big fence and 3 dogs.
1 should be small and ferocious a fox terrier maybe
1 should be very big and salavatingly ferocious anything with rottwieler, mastiff,dane just big.
and the last should be a doberman or rhodesian ridge back.
the first 2 are self explanatory the last ones are for when the crims have gotten into the yard and have found the small yappy dog that has just been suddenly backed up by a BIG dog only to turn around and find a doberman or ridgeback patiently waiting for the show to begin.
I have had ridgebacks for years. the reason they were used for hunting lions is they are just too smart, not saying they didnt get hurt, but they must have had some really smart dogs to go hunting lions with.
there is a dog for every need.... love my dogs....