Shields, on me!

Shields are a fantastic piece of kit.  For most of the history of warfare, shields have been essential to the performance of hand-to-hand infantry and cavalry, serving as the primary defense against all attacks.

The availability of shields on the battlefield informed not only the tactics utilized in the past (shield walls, etc) but also the design and choice of weaponry and the techniques used with them.  Migration Period swords, for example, don't lend themselves well to "fencing", but perform admirably from behind the safety of a shield; the same is, to a limited extent, true with the gladius, and other weapons as well.

GURPS Shields

In GURPS, shields improve your defense in several ways.  Most obviously, they permit you to utilize the Block active defense, which is based on your Shield skill, plus the Defense Bonus of the shield itself - a factor of the shield's size.  This Defense Bonus also improves your Parry and Dodge Active Defenses, as the size of the shield makes your body harder to hit in general - you can be less pinpoint precise with a block and still achieve a defense.  This bonus doesn't require any level of skill in Shield, which makes these objects useful to even untrained fighters; fantastic for hastily raised militia and elite paladin alike.

If utilizing some regular means of accounting for time spent acquiring points, this means a melee combatant can be given the benefit of a shield without spending time learning how to use it; time better spent on things like weapon skill, Shield Wall Training (GURPS Martial Arts p.51) or the Teamwork Perk (p.52).

While the Block skill has its uses, I feel most of the power in a shield as a defensive tool really comes from the passive bonuses.  In addition to improving your active Defenses, shields also act as portable limited Cover (Basic Set p.407), effective against ranged attacks, and quite probably melee attacks as well.

GURPS Martial Arts, GURPS, Low Tech, and Low Tech Companion 2) all improve details present in shields within the game, adding a few options and all kinds of addons, like Lanterns and hooks and whatnot, so there's lots of love for shields in GURPS.

Shields as Passive Defense

I would espouse a shield giving a boost to the defender beyond just the extra DB to defenses.  I would suspect that, so long as the user has a Ready shield, anything behind the shield gains the exact same benefit as cover against ranged attacks.  Really, I would say you get more of a bonus, since typical melee attacks are not going to be able to overcome the typical shield's statistics enough to promote the use of Overpenetration, as given on B408.  You'll have to batter that thing down, first - see Damage to Shields, B484.

GURPS combat - and the combat of every RPG I know - suffers from an amount of uncertainty.  For any object that can move (one's body or parts thereof, their shield, their weapon), one cannot totally be sure where it is at any given moment unless explicitly stated.  This means it is a little difficult to actually say what's behind the shield on the precise moment you attack.  It stands to reason it's probably the Torso when two combatants are coming together, but if they've blocked before (especially to the high or low line with a smaller shield), other parts may actually be exposed.  How you want to handle that - or not - is up to your group.

With certain Hit Locations being behind cover, you'd basically be unable to target them, except at a -10 penalty, as with a ranged attack.  In tactical combat, you could probably reasonably overcome that to some degree by attacking from the weapon side; the rules for Tactical Combat on B390 already penalize shields in that one cannot block with them to the weapon side (which is mostly crap; I'd allow a block at a penalty, at least, especially if Combat Reflexes or something similar are at the disposal of the defender).  That would make attacks at the Vitals - a great hit location for anything stabby - jump from -3 to -10.  Depending on how large your shield is (and how well you are hiding behind it), this may protect everything from around one's Chin to their Knee, quite sensibly.

That accounts for a lot of important hit locations; the shield Arm and Hand, the Neck, the Vitals, part of the Legs and really all of the Torso - so long as they stay behind the shield!

What I am saying is that it is harder to target what you cannot see.  The width of the shield will also play with your weapon's line of attack - back towards the user, the shield's defense area is really more of a truncated cone than just a circle.  Even if you can see it, the attack line may be altered enough that it is effectively in full cover.

Alternatively, rather than going whole hog and calling it concealed (-10), you can utilize the partially concealed rule on B409, and hit locations acquire an additional penalty equal to the shield's DB.  You would, for example, find the Vitals of a Viking warrior wielding a DB2 shield, you would actually target them at -5, as it is behind the "defense region" of the shield, and has a DB of 2.  They would still get an Active Defense!

This is probably the better interpretation, if any are required at all.  If this feels too much like "Double Dipping" a shield's defense bonus (and it may very well be), you could opt to remove the ability to Block if they opt to use the shield's DB as a passive defense.  Thus, if I'm holding the above shield at the ready, the attacker strikes at my Vitals at -5, but it removes "Block" from the options at my disposal - I would then have to Dodge or Parry.

This could also make the Legs and other Regions harder to target; from messing around with sword and shield stuff a bit, someone holding even a modest sized shield out in front of them a little bit substantially effects how easy it is to hit their legs (and head) even without moving the shield much, if at all.

Shields as Armour

It would stand to reason that, a person just sort of holding their shield near their body - and not waving it about - would be due what is essentially an extra layer of armour.  If one would attack the Vitals, you would think the solid piece of wood in the way would absorb some damage as well; that would fall into some of the rules presented on B484 and B409.

This extra armour would probably be void if you tried to Block, as it would just fall into all the subrules of Blocking - only striking the shield officially if the DB improved your Margin of Success to the level you blocked at.

Someone using a Medium Heavy Shield - DB2, DR4, HP16 - and attacked in the Vitals would basically gain DR4 against their covered areas (as agreed upon by the group), and you'd have to erode the shield's HP before you got through.

How it interacts with the above passive use is debatable.

Closing

For more seasoned, reasonable, and well-versed GURPS players and GM's, if I'm not making any sense, what I am basically trying to do is give shields more potency on the defense when you are not actively using them to Block - adding features above and beyond just the Defense Bonus to your Actives they currently provide.

I've nothing against Blocking as an Active.  My first HEMA was I.33 Sword and Buckler, which has it's share of both Active and Passive shield-work, as well as Bashes.  It also utilizes Shields as Armor, as the buckler is used to cover your sword hand.  I find the image of a shield wall of guys actively Blocking incoming attacks...hilariating.  The "Wall" part should allow a user something more than just the shield's DB, I feel.  There's probably a good reason a helmet was the second piece of defensive equipment picked up by hand-to-hand troops after the shield - it's the next easiest thing to hit, since most of the rest of you is behind the shield (GURPS wise the Legs are probably easier).

Then again, Blocking skill could well be the skill of curling up behind the thing as much as it is waving the shield about, and all this is unnecessary.  If so, excellent!  GURPS always has something new to learn about it.

This could well just all be Crap - the current Defense Bonus system may be good enough.  It's something that's been kicking around very basically in my head that I wanted to toss out there, especially since +Douglas Cole put up his recent post about armor.  That guy definitely knows his stuff.

As usual, I suspect even half baked ideas are better thrown up here than left to decay in what little mind life has left me with!

Cheers!