Back in my days training Bujinkan Taijutsu we were taught never to use physical strength.
Pure technique, we were told, could overcome any disadvantage in size or strength. Using
strength would not make our techniques any more effective and would slow our progress in learning the art. Since technique in the Bujinkan is normally practiced exclusively with
compliant partners who are taught to attack and react in a specified manner, this generally worked just fine.

The ideal of relying on technique rather than size or strength exists in judo and jiu-jitsu
as well. Jigaro Kano wrote about using an opponent’s power against him when executing a throw. Helio Gracie actively promoted BJJ as an art where a small person could use skill
and technique to defeat a larger, stronger opponent. Nevertheless, all high-level judo and
BJJ competitors train to be as strong as possible. When students in either of those arts
starts serious randori practice, they soon discover that strength can indeed make a
difference.

To understand this apparent dichotomy between ideal and reality, you have to understand the function of technique in overcoming strength. Technique is not magic, it works on principles of physical mechanics and leverage. If my opponent is 2x stronger than I am, but I can maneuver him into a position where I have a 4x advantage in leverage, then I am effectively twice as strong as he is and I am winning. Typically at the very end of a submission, you should be in a position relative to your opponent giving you a huge leverage advantage sufficient to overwhelm even a much stronger foe. At the moment of executing a throw you should be in a position to apply force at an angle your opponent doesn’t have the balance or body alignment to resist. At the moment of landing a punch your body should be aligned to put your full body weight behind the punch while being at an angle relative to your opponent which makes it hard for him to hit you back effectively.

The tricky part in all this is getting your opponent into the position and alignment which
allows you to have this wonderful mechanical advantage. You can’t just grab him and
physically force him into the bad position, unless you are much stronger than he is. The
commonly accepted solution to the problem in arts such as jujutsu, aikido, taijutsu, and
many others, is to avoid fighting your opponents force with your own. Instead,
practitioners of these arts attempt to blend with an attackers energy and redirect it so
that the attacker ends up in a disadvantaged position. (Surprise and distraction tactics can also be use to help this process along.)

This concept appears to work beautifully when demonstrated on a training partner who gives you a telegraphed, over-committed attack and then makes no effort to compensate as you redirect his force so that he is off-balance and out of alignment. It gets much messier in the real world. A competent opponent who feels himself bringing brought off-balance will adjust his feet to regain that balance. If he feels his limbs being guided out of good alignment, he will pull them back to an anatomically strong position. If he sees you gaining a superior angle, he will move to follow you. He will do this quickly and he will
do it while simultaneously attempting to break your own balance, force you into a bad angle, or just smash your face in the middle of the process.

To complicate things further, if your opponent is stronger than you and not a technical
martial artist he will have no qualms about matching his strength directly against yours to
force you into the position where you are the one who is off-balance, out of alignment, and at a bad angle. If the attacker knows what he is doing with this sort of attack then it
will not be so easy to just blend with and redirect as the stylized and over-committed
attacks you commonly see in taijutsu and aikido dojos. If you haven’t already achieved a
superior angle and position by the time your opponent gets hold of you, then you may be in trouble.

All that being said, technique can overcome size and strength – it’s just more challenging
than cooperative demos would normally lead you to believe. You have to continually adjust to your opponent’s movements more quickly and fluidly than he can adjust to yours. The stronger he is compared to yourself, then less margin for error you have. If your opponent has the same degree of strength that you have, then you can safely engage at a position of equal leverage and attempt to technically maneuver into a superior position. If your opponent is twice as strong as you are, then you can never allow him to engage you at a position of equal leverage because then he could use his superior strength to force you into a position of inferior leverage and then you’re really in trouble. If you want to keep an opponent from ever even reaching a position of equal leverage with you, then you better be a lot more skilled than he is. In my experience, the best and possibly the only way to reach that sort of skill is many, many hours of sparring/free-grappling/live drills with resisting opponents.

There is a trade-off then, between the needs for strength and skill. The more you are
outmatched in strength the more skill you need to compensate (and vice-versa). The
philosophy of jiu-jitsu is based on using technique to beat strength, but that isn’t the end
of the story. In jiu-jitsu competition you are matched up with opponents who have similar
levels of technical expertise and so strength and athleticism come into play. If I have only
a 5% skill advantage over my opponent and he has a 50% advantage in strength, then he is probably going to walk away with the victory. This isn’t strictly limited to sportive
competition. If I am attacked on the sidewalk my assailant will probably not be trained in
jiu-jitsu, but he may very well have practical fighting skills developed in dozens of real
street fights. For me to assume that a street attackers strength relative to mine is
irrelevant just because I am skilled in BJJ would be foolishness.

The precepts instilled during my Bujinkan training time have been useful to me as I have
studied BJJ. I never try to overwhelm an opponents strength with my own in order to force a technique. Nevertheless there are places where strength is useful. Firstly, to keep from
being overwhelmed and forced into a bad place by a stronger opponent who I have not yet found a way to outmaneuver using technique. Secondly, to move my body weight (and sometimes my opponents body weight) against gravity. Thirdly, to protect against injury. Our bodies go through a lot of abuse in BJJ, so a strong core and strong neck muscles can be reduce the chances of getting hurt.

Right now my personal challenge is finding the time and energy to do any sort of regular
strength training when I already push my body’s recovery limits by training jiu-jitsu 5 days per week. I’m still figuring out the best approach for that.