Contrary to a lot of people's belief, shields were used as both an offensive and defensive weapon.

Shield attack video

However your problem is reach and penetration. You can bash an unarmored opponent with a shield fairly effectively or just barge into them with it. However a sword or mace will have more reach and penetrating power than your shield, and a spear or pole arm will be massively more.

There's a reason shield-only fighting was never really a thing. You want your weapon to have some combination of reach, speed, precision and penetrating power. Shields are not good at many of those things.

While this might sound offensive (believe me, it's not), try watching the Marvel movies that feature Captain America:

• Captain America: The First Avenger


• The Avengers


• Captain America: The Winter Soldier


• The Avengers: Age of Ultron


• Captain America: Civil War


• The Avengers: Infinity War

I love watching his action scenes. They're actually quite creative as to what one can do with a shield. Of course we're both talking about an indestructible shield and basically a super human - but this is fiction. Why not, right?

Here's a link to a 12 minute video that shows him in action.

I've seen others comment on how the shield was used as an effective secondary weapon (and it was and would still be). However, since the question is "how can shield only combat be a good idea?" - I will add some real-life historical examples of how people tried (and in one case kinda succeeded) in using the "shield" as both weapon and defense:

Lantern Shields

These we know were real and actually used in at least one duel/street fight, in standard sword/buckler style, and are described as shields whose light was cast only forwards by their being made with an iron plate on that side towards the holders, so that their bodies remained in darkness, had not only the advantage of seeing him when he could not see them, but also dazzled and offended his eyes with the many near lights, which made him mistake those objects that dimly he discerned.

However, there are some weird combinations of these that not only had a place for a lantern but were covered in blades:

^{The above is a real piece from the 16th century, currently at the Kunsthistorisches Museum, Vienna}

Sword Shields

Yeah, why use a sword and shield when you can have both in one convenient package:

^{yes the blade is extendable. yes, this means that the weapon in assasin's creed actually has some basis in reality}

Gun Shield

Okay, there was a point in history where it seemed like they were trying to put a gun in everything. The odd part is though this one "failed" as a hand-held weapon (it honestly can work but I'd hate to try and aim it) - it did have some success as mounted anti-personnel weapons on ships and was a precursor to some modern riot shields and our modern mounted gun shields:

^{Italy, circa 1540 - Higgins Armory Museum}

To add to the idea of gun shields, though modern versions are more a shield with a gun mounted behind it. At least one science fiction show, about a mad man in a blue box, has thought of how it could be adapted in the future to actually be more like its 15-16th century ancestor:

It's all about the combinations

This is certainly stretching the idea of "shield only combat" but all of these are first and foremost shields. So if we allow an extending of the idea of shield only combat to include combination weapons (and use a little hand-waving to bypass the flaws) - its certainly possible.

Less-lethal combat

A shield isn't just armour. The shield boss is a big lump of metal that can be used for bludgeoning. It's also for shoving while in a shield wall.

Your primary use would be riot and general crowd control, rather than combat. Situations where you don't actually want a bloodbath.

Unlike in Holywood movies, melee weapons break when they get banged against other weapons and shields. Fight a long enough battle and you will be left without a weapon, not due to choice but because that's the reality of combat.

Until you can get a weapon from someone else who's out of combat, you will probably have only a shield. If you happen to face an enemy in such a situation, you have no other option but to use the shield.

Here is an example of how to use a shield as a weapon, taken from a famous TV show (warning graphic violence):

Additionally to Tim B.'s very good answer about 'usual' and JGreenwell's covering of 'not-so-usual' shields there is a third category: duel shields!.

They were made for and used as weapons in duels and a form of martial arts was formed around their usage.

On the other hand there was also a wide variety of weapons (mostly daggers) for the explicit purpose of parrying attacks.

In other words: What is a "shield" and what is a "weapon" strongly depends on the context.

I think it certainly is possible to design combat around shields. But keep in mind that the "weapon + shield" combat or the "weapon + defensive weapon" or even a "one weapons suits it all" approach is the result of centuries of developement. Many lost their lives trying something new...

Thanks to JGreenwell! for posting this link: dueling shield manual

It gives a great insight in how dueling shields were used.

You mean like dual-wielding shield? Or One Shield only?

Long Story short: Not realy.

There is no place in history evidencing dual wielding shield or shield only warfare. Someone with a sword (wich wasn't as used as one might think) spears were the most efficient and used weapon, cheaper, VERY effective, you would kill someone with a shield before the shield wilder could even reach you, yeah he may be able to defend against your spear, but for how long? Most people would have a buckler instead of a big shield, than buckler and sword, would be good for moving around on a daily bases.

Of course people would use shields for battles but that'd have their main weapon a side arm, very important people would have a shield bearer, POSSIBLY those shield bearers would use only shields for battles. But a sword and shield would be way more effective, a chair and a shield would be effective, a stone would be used in battle.

There is a reason we have swords, shields, spears in most cultures.

Shield only, single combat? No, that's like playing a life-gaining deck in MTG: there's no way for you to win except by concession of your opponent; lame.

As part of a phalanx it makes perfect sense. First rank shields, second rank swords, third rank spears.

Spears poke anyone too close. Get closer and the shields part so the swords can cut you down. Re-close shield wall. All advance one step. Repeat.

To see this in action go watch the first battle (~45min) in the movie 300. Those shields are too small; imagine them full body size and you probably would need to use both hands. You'd likely have at least a dagger, but your only job is to literally hold the line. If you go down, so do the two others behind you.

I don't know of any historical combat scenarios, but this is Worldbuilding, so:

Shield-only combat facilitates nonlethal combat, which could be used for ceremonious combat, such as challenges for leadership, et cetera. I imagine also it could be similar to types of wrestling, where the shields are used to knock opponents off their feet. It could be useful, as others have mentioned, when there is no other option in real combat. And using only a shield does allow one to carry a second shield for extra defense. Or both hands to increase movement potential.

Possibly, the wielder believes lethal force is immoral and as such only uses the weapon of defense. Also possible would be that the shield needs two hands to operate.

It appears from your question, you are focusing on only single combat even if those singles are in a group. Carrying only a shield or only a weapon was a strong tactic of groups, but is single combat, one usually held one of each for good reason.

While it is possible and is historically proven by several answers here, it is ill advised. If you lose your shield due to damage or disarming, you've lost both your offense and defense.

Back in the day, there wasn't a Stack Exchange so folks had to try to build the one-offs in the hope of gaining an advantage or at least providing a distraction with the novelty.

Using a shield VS a two handed weapon is a trade off between better reach and offence, and more balanced offence/defence.

Your shield-hero could be someone who cares mainly about defence. Huge, pavise-like shields that an ally could hide behind too might develop in an open world that favours ranged encounters, where you can probably see the enemy long before getting the chance to get in mêlée range; in which case missile protection is your biggest concern.

Their offensive capability, then, would rely on moving in a testudo-like formation to advance under fire. If/when they get close, these are going to be your biggest strongest troops so would likely be able to push back enemy lines, or force a breach.

Either way you'd require a counterpart troop, either a shooter or long-pointy-stick-stabber. While your shield-warriors are great at protection, they would lack the actual damage output capability to be effective alone.

Brave are those who charge to the fore with their fortress shields, claiming ground in enemy range.

Strong are those who push back the tide of flesh.

Revered are those who make the ultimate sacrifice, holding until death so that many can flee