It's about the inch punch. You don't swing your fist to punch. The action of swing gives your opponent the time to prepare defence.
To deliver that without swinging your fist, you need strength. I also think Bruce Lee overtraining contributed to his premature demise.
An inch punch when carried out is very swift and spectacular. You can't see the fighter swinging his fist at all and in split second, the opponent is down.
No. I meant this: "...A fight Bruce Lee and..." I think you forgot some words.
Strength is important, but so is technique, if not more so. Good technique imparts extra force. To minimise wastage of strength, the fist is completely relaxed until the point of contact, and without a high level of technique, this is virtually impossible to achieve.
Also important are the development of sensitivity, knowing where to hit, and how to apply leverage. Remember, this particular style was invented by a woman - technique takes precedence over brute strength. Effective application of leverage can diminish a superior force and
unbalance your foe, and knowing the body's weaknesses and being able to easily reach them
(short or inch punches) means your strikes cause greater damage. Wing Chun has "iron rings" training to strengthen the arms; it has other forms of physical conditioning too. However, one should regard Wing Chun as more technique than brawn.
If a drunken ah tiong could land kicks on three poodles, it is not impossible for a very well trained fighter to beat off five people. If Cung Le took on five ordinary Sinkie poodles, my money would be on the former.