Pretty much everyone that has done jiujitsu has heard their sensei or some higher belt say, “technique beats strength.” However, everyone that has trained jiujitsu has been beaten at some point by someone bigger and stronger than them. I’ve seen plenty of high level wrestlers with no jiujitsu experience give high level jiujiteiros a really hard time. Jiujitsu is a physical practice. Martial artists, including jiujiteiros, love to talk about martial arts as having magical or mystical powers, but all physical practices are still governed by physics and physiology, not magic. So when you want to discuss things like strength, leverage, force, technique and mass (size) you cannot separate those things from the laws of physics and physiology.
“The beginning of wisdom is the definition of terms.” Socrates
The first thing we need to do is define some of these terms. Technique is the movements or positions used to accomplish a task. Read more here. Whether the task is a sweep or an armbar, there many techniques that will get the job done. The better technique will accomplish the same task while expending less energy. We understand that when we see newbies using 100% effort to perform the simplest move on someone compared to a blackbelt performing the same move with their eyes closed and talking to someone else seemingly expending next to no energy.
We often view strength as mere contractile potential and a factor that is separate and at odds with technique. That is wholly wrong. Strength is not merely the size and force of your muscles. In reality, strength is the productive application of force: applying the right amount of force at the right time and right direction. True strength is inseparable from technique. If strength were merely about size, you would determine the winner of strength competition by the size of their muscles. If strength were purely about how hard you could contract your muscles, you might see the leg press as a contested event. Strength is directly correlated to the task you are trying to complete. Thus the squat, deadlift, bench, clean & jerk are all separately tested events and the winner of one lift does not necessarily win the others.
Here’s another example: when performing a classic juji gatame armbar, you point your opponent’s thumb to the sky as you pull back on the wrist and bridge up with your hips. The same amount of force (contractile potential) applied with the thumb facing sideways will be ineffective at breaking the arm. Similarly the right technique applied with too little force will also be ineffective. For example, a 5-foot tall, 100lb female trying to armbar a 6-foot, 5-inch tall male athlete that ways 250lbs will likely be ineffective no matter how proficient her technique.
To a large degree, mass moves mass. And to deny that would be ridiculous. This is why we have weight classes in sports. Too large a discrepancy in size and strength cannot simply be overcome with technique. If you want to be competitive, you should not neglect the value of getting stronger. Do not conflate increasing strength with becoming slow and inflexible which is a myth that kept many sports lagging behind the curve for years. Gone are the days when skinny Brazilians can enter the octagon wearing a gi and whoop three people in one night. We now have to train like real athletes and increase our speed and power and strength to be competitive.