What is the "best" defense? What is an "ideal" response? Perfection is usually something that is unattainable and more a matter of opinion rather than some actual definable goal.There are usually pro's & con's to any given response,method,tactic or techniques for a specific defense situation.One approach might have advantages in one area and disadvantages in another.Another might have the complete opposite profile and everything in-between with various combinations.
Also,what is the best course of action for one scenario and it's environment might not be for another one,or it very well still may be.Individuals vary as well in their physical size,age,gender and various skills and these figure greatly into the proper course of action as well.If you are a Police Officer who is 6'6 and weigh 350 lbs arresting a hostile 5 feet 100 lb Female,I wouldn't be too worried about Her picking you up & slamming you on the concrete,but She sure might kick you in the groin or claw your face.If your a 5'6 Man being attacked by a guy over a foot taller & twice as big,you will take a different approach than if the physicality were reversed.
Don't let perfection be the enemy of the good is a common phrase in politics and the concept applies very readily to many defense scenarios.Meaning the "ideal" solution for staying safe is to escape,but attempting an escape may not be the best idea such as they are drawing a firearm(in an open area)and are in a blind rage(you run,you'll probably get gunned down).A parry moving to the outside to set up a finish might be an "ideal" response,but maybe you misstepped or lost your balance and have to simply cover up being in a bad position.Maybe you get knocked down by a knife wielding assailant and you have no time to do a "proper" defensive technique and end up taking a stab to the forearm. Not ideal,but better than getting stabbed in the back or something as bad if that's what it prevented. Some techniques are more "risky" than others.I would say that an obstruction type shielding block is usually more likely to stop the attack for sure(percentage wise)from reaching it's intended target,but it may also put your limb at risk for serious injury plus doesn't usually set up or put you in position for a counter.A parry redirects the blow and sets you up well position wise and may even off balance them,but it may be harder to apply and can have a greater percentage risk potential for missing.
My "ideal" defense techniques are usually evasion(slipping to advantageous position/angle etc. with perhaps a parry AND a cover/shield block as a back up.Redundant,but effective and all selections depend on the individual situation dynamics.Evasion by itself and counter might be what's needed or a parry only or a evade with a back-up shield and counter.There is realistically not a one single best answer for all possible scenarios.Of course,a jamming technique or stop-hit is better if you intercept/anticipate his technique by reading body language/see any telegraphing or perhaps simply evading(creating space in any direction)for escape etc. appropriate method depending on the specific situation.Some say make him miss(slip/evade)by only the slightest of margins so he can't react and your in a good position to counter.While probably true most of the time(especially in unarmed fighting),it might not always be the best idea.How about when He has a knife or a baseball bat? Creating a lot of space puts you farther away for a counter,but it also puts him farther away for a follow up.If your needing to draw a firearm against an assailant,then space and creating it is usually what you want to do to give you time to draw.Perhaps you have to perform a unarmed defensive move against a knife armed attacker and to do otherwise most likely would get you stabbed before you get your gun out and you have no space available to create distance.The variables are virtually endless.What if He is much faster than you,stronger,bigger,younger? This all figures in as well.Proper techniques & tactics overcome much of this.Using set-ups,timing,angles and combinations can negate speed just as leverage can overcome strength,but is usually better to not fight against their strengths.You want to maximize you strengths and minimise his while maximizing/exploiting his weaknesses while avoiding yours.If I'm a great striker and terrible grappler,I wouldn't probably shoot in on someone I know is a good wrestler.Just like you can't use a reach advantage against someone who has a longer reach and is taller.Being bigger stronger,stronger,faster generally offers/allows you more options than if you didn't have those advantages and you should exploit them when able to.Conan Silveria vs Sakaraba-Conan fought like he was a small man fighting a man that was 100 lbs bigger.He didn't use his size advantage and approached the fight as if He was Royce fighting Severn and had to worry about a slams and throws(Laying down is not a good strategy or acceptable option to avoid being thrown/slammed.Royce won,but was mauled for 15 minutes.Had Severn had any offense at the time,Royce would have been destroyed.MMA fighters have learned much since those days).
And just because your smaller than opponent doesn't necessarily mean you are limited in your options or limited at all as technique and skill and negate much & How great is the size difference really? Hackney vs Yarborough was an outrageous difference,but that is not likely to happen in the real world.The idea that you will be forced to fight from the guard(and worse stay there)just because the opponent is a lot bigger is complete nonsense.Belfort fought many a larger opponent,but never went to the guard.Couture didn't lay down for Sylvia and Fedor never lays on his back in guard against the monsters he has fought.I feel the guard is the WORST place to be against a much bigger/stronger opponent.A bigger guy can really devastate you from the top.It allows him to use his weight and strength via gravity and your body being brace by the floor to his advantage as well as your mobility being limited and his being open.You may be forced to the bottom,but you want out and should never willingly stay there except in the rarest of circumstance although I can't even imagine one in which it would be the best course of action or even a good idea.
For any situation,you have to determine what your primary goal(s)are.First should always to not get hurt or injured and to avoid actual conflict thereby avoiding risking physical injury. Then the specific details of the scenario come into play to determine what the best overall strategy would be.How many people are there?Are they armed?Is your Family with you? etc.
Some combatives "experts" advocate always engaging or going forward,but this idea is extremely flawed.If somehow has a knife and you attempt to disarm, but end up in a bad position,it may be better to create space and simply reset rather than fighting from a bad angle.This concept would be the same idea as shooting in for a double leg takedown and mistiming it and getting strung out.It may be better to create space and reset rather than trying to force to takedown.If someone is attacking and you are moving backward,then yes,they are gaining momentum,but that momentum can be used to your advantage to set up a takedown or perhaps slip out to the side using evasion and a parrying type movement and their momentum off balances them to put you in prime position for a counter or an escape.Moving backwards might be the right choice or the wrong choice depending on the situation.You have to train the variables & options to get a feel & idea of what will and won't work in different scenarios.Most of the time it's best to not keep moving back indefinitely(unless your are simply backing away from a confrontation not currently active and are keeping on guard),you either turn and run or engage and employ offense depending on the circumstances.At some point you'll likely want to utilize a Tactical-L,evasion,parry etc. with a counter.The time to do so depends on the dynamics,what's available,if you set him up and/or in a position to execute it yourself.
If a guy has a gun,then once the distance is closed and you are in a contact situation,you want to keep it and try to get control of the gun and disarm.To create space in this situation would be suicidal.Of course in the reverse,if there is a fair amount of space already,it's better to run(chaotic zig zag pattern) to cover or escape.Everything has to be in context.Of course in a mugging or robbery,it's usually better to comply if possible and only engage if it looks like they plan on shooting you or are trying to take you away from the scene.
Many Reality-Based Instructors will speak about the need for Direct & Decisive actions & responses that end the confrontation quickly.If there is a conclusive solution available to stop the attacker or escape the situation,then using it would seem to be the most logical response and the less time that your at risk would seem to lower the risk overall.However,many so-called decisive actions put you at just as much negative risk as it does positive resolution should the decisive action fail that it might not be the best option and a less risky alternative may be a better choice.Running away from a knife wielding assailant sounds like a good plan,but what is He's faster than you and repeatedly stabs you in the back.Before letting that happen,it's probably better to turn and fight and perhaps look for another avenue of escape. A particular hard to apply grappling move or certain hard to land type of powerful strike might very well be able to end the fight,but it may also cause you to lose position or open you up to a counter should your technique fail.It might succeed and might be the ideal technique for a specific situation,but a safer alternative to set it up may be necessary.There even may be a direct decisive action/technique/combination that is safe AND a fight ender for that specific scenario.It also might be a single technique or a certain combination.It's dilemmas such as these as to why self-defense is more of an art than a science even though we use many scientific principles.