Rules Nugget (GURPS): Shields and Cover

Intro: Under Cover

This rule looks at the matter of letting shields provide cover instead of a DB bonus. That option offers some interesting benefits, from a nicely-restored (in 4e) ability for shields to protect passively, to detailed protection by body location, to shield walls and other defensive tricks. It all meshes nicely with existing game rules for cover, too.

The rule

In general, treat shields as offering only their DB, per written rules. But whenever the GM thinks it sensible, treat shields as cover (B407) instead:

• A shield treated as cover offers a TH penalty equal to the shield's DB, instead of adding DB to Active Defenses, for any attack against which DB would be effective.

A shield protects with either its cover or its DB, not both at once. If it protects as cover and the TH penalty causes the attack to fail, the attack struck the shield, with no additional action on the part of the defender. If the attack succeeds, it strikes some area not covered by the shield.

Example: You hold a shield with DB 3. Treating this as cover, enemy attacks take -3 to hit you. An attack that fails by 4 or more misses you entirely. A attack that fails by 1 to 3 strikes the shield. An attack that succeeds bypasses the shield and hits you.

Defending

When an attack treats a shield as cover, the shield wielder can attempt any normal defense, even a Block – but defenses do not get the added bonus of DB.

Variants and options

Ways to treat cover

There are several ways you can game shield protection as cover. The suggestions below allow for extra-high DB from unusually large shields, or from curling up behind a shield; these are combat options offered in Shields and Size.

Abstract cover

This is the default used in the core rule above. For simplicity, use shield DB as a TH penalty versus any location on the target; don't worry about specific cover by location. 

Random cover

An alternative to the above: Per B408, you can give attacks a random chance of striking cover, instead of using a TH penalty. For example, rather than a -2 TH penalty, half cover applies a 50/50 chance (4-6 on 1d6) that the attack will hit the cover.

Here's an expansion of that:

No cover: Doesn't significantly hide target. No effect. Example: DB 0 "shield".
Slight cover: Hides 1/3 or less of the target. Treat as -1 TH, or as 2 in 6 chance of striking cover. Example: DB 1 shield.
Half cover: Hides about 1/2 of the target. Treat as -2 TH, or as 3 in 6 chance of striking cover. Example: DB 2 shield.
Good cover: Hides 2/3 or so of target. Treat as -3 TH, or as 4 in 6 chance of striking cover. Example: DB 3 shield.
Excellent cover: Hides most of target. Treat as -4 TH, or as 5 in 6 chance of striking cover. Example: DB 4 shield.
Full cover: Hides all of target. Example: DB 5+ shield.

Specific cover

Yet another alternative to the above. Specific hit locations gain full, half, or no cover from the shield. Full cover makes a location impossible to hit. Treat half cover as above: -2 TH, or 3 in 6 chance of striking cover. Locations not mentioned (e.g., face) gain no cover and can be targeted at their usual penalty.

DB 0: No significant protection for any location.
DB 1: Half cover for shield arm/hand (full cover for shield hand if buckler) and torso/vitals.
DB 2: Full cover for shield arm/hand; half cover for torso/vitals/groin.
DB 3: Full cover for shield arm/hand and torso/vitals/groin; half cover for legs (but not feet).
DB 4: Full cover for shield arm/hand, torso/vitals/groin, and legs (but not feet).
DB 5+: See All about full cover below.

Using specific cover means that an attack need only target an uncovered location – such as the weapon arm, at no penalty beyond the usual -2 – to negate shield DB. On the other hand, some locations become completely covered, disallowing attack. Overall, specific cover provides a fair tradeoff compared to the abstract and random treatments.

Ambitious and detail-hungry GMs could further expand specific cover effects, using the entire range of possible cover (no, slight, half, good, excellent, full) for each body location, and even further modify per-location coverage for shield position (i.e., held high, "normally", or low). I leave that to the interested!

All about full cover

While a defender cannot actively wield a shield with DB of 5 or more, he can hide behind it to gain full cover for all hit locations. As above, this means the locations cannot be hit.

DB 5 fully covers the defender, if not optimally. It provides full cover from the front center hex only, and the defender must remain still. Attacks from the left/right front hexes, lobbed attacks, or any shield wielder movement render cover incomplete: treat as excellent cover (-4 TH, or 5 in 6 chance of striking cover).

DB 6 allows full cover from any front hex and even allows minimal wielder movement behind the shield. (Whether and how the wielder can prop up such a huge shield in the first place is a GM call.)

At DB 7 and larger, we're talking big propped-up walls behind which the defender has plenty of room to move. Handle accordingly.

The GM will rule on any special considerations. A melee fighter could run behind a covering shield to get at the defenseless wielder – or possibly even reach his weapon over the top of the shield from the front. A very small fighter behind a large propped-up shield may have full cover versus enemy shooters, with room to move about too – but if he pops out from behind cover to return fire, he'll be partially exposed in that instant. And so on.

Protection and facing

Per written rules, a shield offers protection only versus attacks from the wielder's front center hex and shield-side hex. It provides no protection – DB or cover – vs attacks from the weapon-side hex, side hexes, or rear hex.

An exception: As described above, DB 5 and larger shields used as full cover can provide full or partial cover from all three front hexes.

Cover and flails

It would make sense to reduce the cover value of a shield vs a flail or similar hard-to-block weapon. Use the Block penalty as an effective decrease in levels of coverage, i.e., a reduction in the TH penalty.

Example: A flail that gives a -2 to Block attempts treats a shield offering good (-3 TH) cover as offering only slight (-1 TH) cover.

Notes for GURPS 3e

All of these rules will work with GURPS 3e too, with one change: Subtract 1 from a shield's PD, and use that as DB in the above rules.

Example: A medium shield offering PD 3 in 3e has DB 2 in 4e terms. It acts as a DB 2 shield for all purposes above.

Connections

Shields and Size

As mentioned above, these rules work especially well with the Shields and Size rules allowing you to boost DB by hunkering down behind a shield, or by borrowing the shield of a bigger creature.

Here's an extra nugget for users of both rules: Let Shield-Wall Training (Martial Arts 51) remove the left/right front hex vulnerabilities of DB 5 shields when trained wielders act in close formation (i.e., a line or circle, one man per hex). That's the way to build an impenetrable "turtle" formation: Take large DB 3 shields, have fighters "hunker down" beneath to gain a +2 DB bonus and the full front-hex cover of effective DB 5 shields, and let Shield-Wall Training ensure that each vulnerable right/left front hex is covered by the next man. Do that in a circle, with fighters in the middle taking care of the "roof", and you've got a "turtle" dome protecting every angle. SPARTAAAA!

When to use it

GM choice

When does a shield provide DB, and when does it provide cover? It's a GM call. There's nothing particularly wrong with the existing rules for shields and DB, but cover may play more realistically in some situations.

For example, using the specific cover rule, you may find it more realistic for a shield to provide great protection to the torso and partial protection to the legs, while leaving the head or feet fully exposed, instead of granting equal protection to all locations.

If you don't care for a wholesale switch to shields as cover, you might use the rules in limited instances. The full cover rules come in particularly handy when a character wants to curl up behind a shield – it's a great defense versus ranged attacks like arrows or dragon fire.

Another good use for the rules is any instance in which a shield user has no active defense versus a ranged attack. Currently, even a large shield offers no protection against an unseen arrow in 4e, as it only aids in active defense. Cover rules allow a chance for passive protection too.

Example: A silent crossbow bolt streaks toward an unsuspecting knight with a DB 2 shield. Whether the arrow intentionally or randomly targets a specific hit location, the attack suffers a -2 TH (using default abstract cover), or has a 50/50 chance of striking the shield (using random cover), or attacks the head normally, the torso with partial cover, and the shield arm with no chance of avoiding the shield (specific cover). Although the knight has no Active Defense, his shield may catch the missile.

Attacker choice

Optionally, an attacker can choose to treat a shield as cover. He's specifically aiming to strike far from the shield's protected areas, negating its extra protection. Using default abstract cover, that means an overall TH penalty. Using random cover, he takes no TH penalty, but stands a random chance of striking the shield. Using specific cover, he simply has to choose a hit location that's not fully covered.

If the attacker hits, follow rules as above: the defender can defend (and even Block) normally, but doesn't add DB to defenses.

Status

This page separates shield cover rules from an earlier page combining them with the rules for wielder size and position. Both of those, in turn, come from outdated GULLIVER rules for Shields and Size.

My old 3e rules worked fine for me, but this is an all-new update for 4e, with a few new and untested tweaks like the note on flails. It all needs more scrutiny and testing!

Designer's notes

1. If the GM allows fighters the choice of whether to handle shields as DB or as cover, my old GULLIVER rules suggested that either the attacker or defender could make the choice. I removed the defender choice for this update; it seems more sensible that the attacker would be the one to decide, by choosing to expressly aim for uncovered areas. What do you think?

2. While we're on that topic: It would make sense that an attacker is always trying to strike somewhere unprotected by the shield, as opposed to making a special choice to do so. But since there's no default TH difference between hitting a shield-protected target and an unprotected one, we can assume that the default blow isn't a particularly concerted effort to do so. The above penalized blow does mark a concerted effort to get around the shield, whatever exactly that may mean in the abstract positioning of combat.

The ruling seems even more sensible in the case of ranged combat: either you aim a shot at the target in general, in which case you might send your arrow directly into his shield; or you deliberately aim for some smaller, unprotected part. The latter is a tougher shot, but unless the target responds with a skillful Block, a successful hit guarantees you're not haplessly plunking your missile into that darned buckler.

3. These rules let you treat a shield as cover, and optionally let an attacker bypass that cover (i.e., negate the shield's DB) by taking a TH penalty. That all plays nicely with 4e's written rules for cover.

But the net effect of bypassing DB by taking an equivalent TH penalty (or by aiming at an unprotected area, depending on how you play it) bumps up against one other rule: the Deceptive Attack. That action could also be employed to simulate "bypassing" shield DB – but it would charge double DB, not straight DB, as a TH penalty.

That had me thinking: Should these rules use double DB as the TH penalty for cover? Doing so would put things in line with the Deceptive Attack rules, yes – but would then conflict with the rules for cover. A half-covered target only applies a -2 TH in 4e, which seems to play nicely with the game's 3d hit probabilities as well. Using doubled DB as a cover penalty would imply that a small DB 1 shield or cloak covers half of a human, and that a medium or large shield covers almost all of a person. That doesn't seem right.

In the end, I favored conformance with 4e's cover rules, as cover is the topic at hand. Yes, this means that if the GM allows you to treat a target's shield as cover, you can essentially take a "cheap" Deceptive Attack at only -1 TH per -1 Active Defense, up to the target's DB (further decreases in Active Defense would carry the usual, higher TH penalty). That marks a break from the standard treatment of Deceptive Attack as a way to reduce defenses.

That's using abstract cover, though. I think specific cover plays more nicely with Deceptive Attack. You can avoid DB entirely just by attacking an unprotected location, but on the other hand, some locations will be fully protected; you can't attack them at all. It makes for a different dynamic.

The GM could then allow Deceptive Attack, at the full -2 TH x shield DB, as a difficult way of getting at the fully protected targets – say, a sword thrust from above that goes over and behind the top of a large shield, to get at the (normally) fully-covered vitals. That preserves a special role for Deceptive Attack as a way of getting past shield protection. It's a thought, anyway; it should be rigorously tested.

Wrapping Up

The above offers a lot of shield stuff for the GM toolbox, but there are decisions to be made: when to treat shields as cover instead of DB, and which treatment of cover to use (abstract, random, or specific).

What looks useful, not-so-useful, or just plain broken in there?