You don't need to have a dog from puppyhood to have a connection with them. I got my older female when she was three and a half, and she knows who her mother is. She sticks very close, she enjoys her work. Her job is to watch out for trouble when we're out and about. She carries the poo when we are on hikes (she rolls in cow pies... >>).
You want to consider what kind of access you have when you are looking into getting a dog for personal protection. That is not something that you train by yourself. You want to be sure that you have a trainer who you can work with that knows what they are doing. And just like with most jobs that you have for dogs, it is going to take a certain dog to do it. Truth is that most of the time, you just need a dog to look super scary, not necessarily go for somebody.
My first dog was never really trained, but I loved to answer the door holding her collar when I didn't know who was on the other side. The sight of a 100 lb dog barking and growling at you is enough to make the average person pause easily enough.
Others probably can weigh in more, but I just wanted to say you don't necessarily need to have a dog from a puppy for them to love you and want to protect you. You simply need a bond with the dog.