Secure him to a leash and then walk him around the area you want him to protect. Do this once in the morning and once in the evening. You are reinforcing to him where his boundary begins and ends. He’ll naturally feel more protective of anything inside his territory.

Now secure him to a long leash. Tether it to a point where the object you want him to protect falls within his space. Again, the long leash will reinforce where his territory reaches.

Whenever you see any signs of defensive behavior, reward him. You can give him a treat or play around with his toy for a few minutes. You can also shower him in verbal praise. Any barking is precisely the behavior you want to see.

Boxers can have a temper so it’s important you don’t ever shout or scare him. If he’s terrified of you then you may find it harder to toe the line between defensive and aggressive.

After a couple of weeks of boundary training, have a stranger approach slowly. If your dog barks then give him a treat and lots of practice. Practice this every few days with different people until the habit becomes cemented.

Spend a couple of days watching him for situations where he naturally barks. This could be just before you go out for a walk or when you’re preparing his food. You’re going to use these moments to teach him to bark on command.

Now in those moments, start giving a ‘bark’ command. As soon as he starts barking you can give him a treat and lots of praise. Practice this for a few days.

After a few days he’ll associate the command with the behavior. Now you need to practice it when he’s not already naturally barking. Again give the command and then a treat. Practice this until he’s fully got the hang of it.

Now have him sit in the place you want him to guard. Then have a stranger approach slowly. When he reaches a certain point, give the ‘bark’ command while pointing at the person approaching. As soon as he barks, give him a treat and praise.

Practice this every couple of days but change the person that approaches. Try and use people he doesn’t already know. Once you’ve done this for a week or two it will soon become habit. You will then have your guard dog.

Enroll him into dog training classes from a young age. Not only will this help discipline him to respond to your instructions, but it will also mean he remains friendly and sociable. You don’t want him to be unable to spend time with other pets and humans.

Have people he doesn’t know approach the door. If he knows them already he probably isn’t going to bark or be protective.

When they do knock, point at the door and get animated. You need to draw his attention to the person approaching and encourage a reaction. This hurdle will be the biggest. You need to convey to him what you want him to do. Keep encouraging until he barks.

Now have the person outside shout and run away. It’s important he hears them leaving. This will signal to him that he needs to bark until he hears them flee.

Once they have run away give him a treat and lots of praise. Now practice this every few days. As he gets the hang of it you can give him less and less encouragement. It will soon become habit to bark at them.