Training is considered highly necessary for all guard dogs, as control of the dog is necessary, and the dog’s inexperience can affect its effectiveness in an unexpected situation. Factors such as not knowing how to react to the invasion of a strange person, fear of a new situation, inappropriate biting technique and lack of self-confidence, all caused mainly by inexperience, are reported in real cases where the dog was ineffective. Only in rare cases of phenomenon dogs with naturally very high self-confidence have certain inexperienced individuals managed to repel intruders, but often without the most effective biting technique, lengthening the fight and bringing harm to both. When training a guard dog, the professional trainer and the helper (who wears protective clothing and is bitten by the dog) seek to desensitize the dog, showing new situations with people, objects and sounds, gradually increasing the stress level, increasing the dog’s self-confidence, inducing the best way to react and where to bite, improving the biting technique so that it is lasting, firm and with a “mouth full”, and adding control commands, such as commands to attack and to interrupt the attack. In cases where the most common intruders are humans, such as in urban areas, medium to large guard dogs are trained simply to suppress or immobilize the intruder by biting the upper or lower limbs and interrupt the attack under the command of their owner, when he arrives.