This is going to be a bit of a rant.
People will tell say that blocking is useless, that blocks don't work...
OK. Then why the hell have all of these combative systems continued to include them, for anything ranging from hundreds of years to thousands of years? Bando's roots trace back thousands of years, but the modern version was gathered by U Ba Than and many others in the 1940s. They were all combat veterans, and ruthlessly insisted on techniques that worked. Dr. Gyi has shared the story of how someone brought a beautiful stick system, and claimed it could defeat 10 men at once. They put it to the test, and it failed. Now, we don't know what it looked like. But blocks stayed in the system.
Joe Manley has consistently taught, for at least 25 years, with a huge emphasis on defense. On using blocks and parries. So has Lloyd Davis. Both were feared fighters, whose skill today is often (I think) underestimated and misunderstood. They trained champions who trained champions.
Look at other systems, and you'll find they all have blocks. Blocks, therefore, must have the potential to work. So why can't people make them work properly?
Here are a few of my thoughts on it. Take 'em for what they're worth.
First, let's look at the term: block. In Japanese, I know, the actual term is really closer to "receiving." Lots of people try to make a block work by staying there, and flinging their arm at the incoming attack. Well, you've already got one problem, there; you're behind the curve. Action beats reaction. So now your arm has to be faster than their punch. It might work, if you're fast enough. But are blocks really meant to be a stationary technique, simply accepting the hammering of the block?
Not the way I was taught. The start of the block is EVASION! Moving the target to assure that you're safe, then insuring your safety with the block. Letting the block punish the attacker for intruding on your space, because you're already safe.
That lets me segue into the next thing: timing. Too many people try to block the attack by waiting for the it to come, then deciding what to do. Let me bring a new term in: OODA Loop. In short, Colonel Boyd realized that for us to respond to something, we must first Observe it, Orient on what it is, Decide what to do about it, and finally put into Action. In practice, in fighting, if we spend too much time trying to figure out what's coming, by the time we can recognize it and decide what to do, we've been hit. The fix is easy to say -- Movement is movement, and when you see movement, MOVE!. After that, from a safe place, you can take your time to catch up. (Yeah, easy to say. Hard to do! And it takes a lot of painful practice to achieve for most people.) Blocking takes place, ideally, when you're already safe.
Finally... I think there's an issue about committing to actually developing the skill. It's easy to try something once or twice, then jump on the "It doesn't work" bandwagon. Developing skillful blocking is hard, and you will get hit sometimes as you work on it. Lots of people don't want to get hit, they don't want to submit their ego to the learning process. It's not fun! But the results are worth the pain.
So... to summarize... Why the hell did all of these combative systems maintain blocking and defensive techniques if they don't work? Or, maybe, are they not working because we aren't doing them right?