There are two different types of submission, lifestyle submission and erotic submission.
Sociobiology. The knight is brave, strong, and capable, but genetically programmed to submit. Your modern knight is chivalrous, which in modern terms means he submits to a higher moral code. He is fair and kind, and he feels guilty more than he should. Your submissive knight is also desperate to submit to a female. When a man falls in love, a very common fantasy is risking his life to protect or save the woman who is the object of his love.
So, men are programmed to submit, some more than others. Some men do not fall in love. Some men are very submissive.
Women can enjoy submission too, but they are genetically programmed to command. The stereotype of the female is weak and passive, but that's just at the start of the relationship. Sooner or later, women take control and manage the family resources to provide for home and family. The knight is one of these resources. By taking control, a Dominant accepts responsibility for another person's life. Women do this whenever they have a baby.
Also consider competence. Men are better hunters and do not need a woman's advice on how to hunt. In general women have better social skills, which would lead them to be leading in many interactions with her mate. Women are also a little more cautious and preparing. These are good traits for a leader making decisions for the whole family.
This is a sociobiological theory. The male is submissive because submissiveness is adaptive; the woman is dominant because of her dominance is adaptive. We are supposed to have a patriarchal society run by dominating men. Well, the knight should not submit to everyone, he is supposed to rule corporations. He submits only to his mistress. So he seems dominant and is dominant, except to his wife. Women are attracted to the strong knight, that's their programming. So at the start of the relationship, the man must appear as strong and dominant as possible. If he is later to submit to this woman, he might be programmed to select a caring woman. So in the start of a relationship, the woman's best strategy might be to appear caring. So men are dominant, except to their spouses.
The tendency to submit. You submissive tends to follow orders and wants to please others. That's his personality. Of course, everyone considers consequences, and the best action is often to follow an order or please someone. But the submissive tends to obey or please before any conscious thoughts. Submissives might be more attuned to others' feelings, and that they hate conflict, which is why they want to obey and please.
Your submissive might not be this way, but you can't know just by looking. The submissive learns to defend himself, so he does not submit or try to please every one. But this takes a toll on the submissive, and you should appreciate that problem.
The desire to please his Mistress is probably adaptive. Consider the ancient hunter. The single man could hunt because he was hungry. The man with a mate and family needs another motivation, like pleasing his mate. Perhaps, in the world of the male, nothing is more important than pleasing his mate.
Implications. Submissives have a strong need to submit. If he can't submit to you, he will be very unhappy or look elsewhere (and be unhappy). So you should think carefully before turning down a dominance gig for your knight. Your approval is also very important. If he does something useful for home and family, such as bring home a paycheck, show him your approval. Not just the word thanks, but at least a smile and a happy thank you.
The ideal job for a submissive would involve pleasing a boss, who would show approval. Avoidance of personal conflict is also probably important. He should not have to deal with people who do not care about him. He can defend himself against these people, but probably not perfectly, and not without suffering. Because of his high moral code, he should have a job that helps people, or second choice at least a job that does not hurt or take advantage of people.
The second type of submission is erotic submission, and it is very important to men.
Kinks and fetishes. The loss of control is erotic. The kinks and fetishes of submission are everything the submissives have found that causes loss of control. Bondage is an obvious loss of control. And submission is the loss of control. The offer to submit is an offer to give up control, the desire to submit is a desire for no control, and complete submission is a complete loss of control.
Perhaps the most common kink in submission is the desire to be humiliated. The School of Caring Domination believes that humiliating a man lowers his self-esteem and feelings of worth. With less self-esteem and worth, his willpower is decreased. This is exactly what the submissive wants, because less willpower means less self control and less ability to resist domination. In short, it can be erotic to the submissive. But the loss of self-esteem and worth is bad, so much of caring domination revolves around avoiding humiliation. There will be an entire lesson on this. Rejection and criticism also can be erotic, and again they lower the man's power.
Why? Why is a loss of control erotic? Lets start with erotic. Duh, something is erotic because it increases desire. But desire is a loss of self control. If you desire sex, you are losing your self control to work or avoid sex. You might not notice your loss of self-control, because you just want sex, but it's gone. So, in a funny way, being erotic means loss of control. Being taken over by the desire for sex, is found throughout the sexual act. The ultimate in arousal is complete desire for sex. And it is impossible to tell a story about a good orgasm where the person does not lose control.
The male is programmed to find the female body erotic, and he is programmed to be aroused by physical sensations. The male might be programmed to find the loss of control erotic, but this is probably learned, by association and conditioning. Like how smiling helps make you happy, the loss of control is erotic to the submissive.
More kinks. Teasing is also erotic to the submissive. Teasing is the suggestion of sexual delights followed by their withdrawal. Teasing leaves the man in a state of frustrated arousal, which might sound unpleasant and is, but it is also a state of strong desire. Another submissive fetish, believe it or not, is enforced chastity. Everything can have different meanings, and chasity can be humiliating and signal submission and a loss of power. But it also increases desire. The stereotyped dominatrix wears provocative clothing, which of course increases desire.
Guilt. The stereotype is that the submissive feels guilty, so he wants to be punished. By pain, humiliation, spanking, whatever. In my experience, this is not true. The submissive is after submission and sex, not punishment. Anyway, if someone wanted to be punished, what does that have to do with sex?
Of course, the submissive does feel guilty. The submissive has a high moral code and is sensitive to others, so he always feels guiltier than he should. His kinks and fetishes just add to this guilt. Meanwhile, guilt is probably one more way of making a person weaker.
The cruel dominatrix. The submissive wants to submit, he wants arousal, he wants sex. He is supposed to submit to the caring woman. He knows that. But he doesn't have a caring Mistress, and he really wants the sex. So the cruel dominatrix will do just fine. His high moral code and his willpower stop him from obeying the cruel dominatrix. but he doesn't want that protection, so he craves the loss of willpower.
Some men want erotic submission and have no interest in lifestyle submission. In my experience, they like to be the one who is really in control. This is called topping from the bottom, which means controlling the situation even though pretending to be the sub. So you have to watch for this, at least if it is not enjoyable for you. Just to guess, you might really be able to do noncaring things to these men, since they are not really submitting. So you could probably withhold sex/scenes unless they do what you want.
But most submissives want both, which is probably fair. The knight is supposed to submit to his Mistress, and in return he has the pleasure of seeing her happy and approving of him, but he probably deserves good sex too.
Most of the time, the man's immediate reason for seeking domination is that he wants erotic domination. You are probably more interested in lifestyle domination. Erotic domination is measured by how excited the man is to obey and be controlled. Lifestyle domination is measured by how much he wants to please his Mistress and make her happy. Those are two different things. But if your knight is submissive, and if you can erotically dominate him while being caring, the lifestyle domination will follow.
Unfortunately, many of the tricks for erotic domination work against the lifestyle domination. A recurring issue is how to erotically dominate your knight without undermining your lifestyle domination.