This is a big one.
In the modern age, in the United States, I'm not sure how much this makes sense. For years I told people "Get a Glock and learn to shoot."
I understand many people who believe in having dogs as protectors have noble intentions and they mean well.
But unfortunately if your dog is ever called to protect you, the likelihood that they will get seriously injured or die themselves in the process, is actually pretty high.
Are there dogs who are well suited for protection? Absolutely!
But those dogs are relatively rare, all things considered.
And most dogs, when they are tasked with protecting their homes, exhibit poor judgment. (Growling at your company that you've known for 30 years).
With extensive training (think 1 year or more) some dogs can handle that position responsibly.
But your dog isn't likely to accidentally become a well rounded protector.
We should always treat aggression like it is: a ticking time-bomb that could very seriously end up costing us $43k (average court award in the US) and the dogs life.
Our dogs need an opportunity to outsource fear, frustration, and anger to us.
I'm reminded of a story I heard years ago.
A gentleman was tired of worrying about money so he hired someone to do that for him.
In 1 day he went into $1M in debt. His neighbor asked him "Wow I didn't realize you were so rich" to which he replied "Oh, I'm not. I'm in debt up to my eyeballs."
And the neighbor says "Then how will you afford all of this??"
And the man says "oh that's not my job to figure out. I hired a guy to worry for me."
Your dog deserves to be able to outsource their fear and worry to YOU.
Don't EVER discount any amount of protection, guarding, etc. It's your dog telling you, out loud, that they don't believe you can or will handle it.
And you don't want to find out the hard way that they've assigned the "protectorate" role to themselves.