NOVA

The Vikings were some of the fiercest warriors of all time,

and a select few carried the ultimate weapon:

a sword nearly a thousand years ahead of its time,

built by a mysterious craftsman

from a material unknown to rivals for centuries.

The sword was known as the "Ulfberht."

The swords were far better than any other swords made

before or since in Europe.

The secrets behind its design, creation and use

have been lost.

But now the world's largest steel company

and a modern-day blacksmith divine its mysteries

and bring the Ulfberht back to life.

To do it right,

it is the most complicated thing I know how to make,

and it's that challenge that drives me.

A millennium after its time of glory,

discover "The Secrets of the Viking Sword"

right now on this NOVA/ National Geographic special.

== sync, corrected by elderman ==

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Master swordsman John Clements

has cut with some of the most famous swords ever made...

...from Damascus steel blades

to the legendary samurai sword, the Katana.

Forged by master craftsmen from the 14th century onward,

the samurai sword is renowned for its elegantly curved blade

and impressive cutting ability.

I think the Katana is a beautiful weapon,

it's a fine weapon.

It slices, it cuts, it thrusts, it dices,

it makes julienne fries, it's wonderful.

But it has been exaggerated.

Exaggerated because sharpness alone is not enough.

So you see demonstrations of a sharp sword like this

cutting material all the time and you think it's impressive

because, "Ooh, look what it does!"

But that's really not that impressive, and here's why.

This is a wide medieval bastard sword, and this one's blunt.

It's got no real edge to it.

No edge sharpness.

But watch what I'm going to do with it.

A really good sword is not just about cutting

with a really sharp edge.

Strength, flexibility, weight and shape all determine

how well a blade meets the combat challenges of its time

and whether it's a superior sword.

Many great swords are famous,

but there's one few have ever heard of

that was perfectly designed for its day.

They were a luxury: rare and expensive.

It was the Rolls Royce of the swords.

Produced only from about 800 to 1,000 A.D.,

this Viking sword was made from a pure steel

not seen again in Europe for nearly a thousand years.

This high-tech weapon of its time

was inscribed with the mysterious word "Ulfberht."

Carried by only elite warriors,

the Ulfberht represented the perfect marriage

of form and function in the chaos that was a Viking battle.

It's not people divide you up and have a nice duel one-to-one.

The fight was very violent.

Chaos.

People moving around,

striking out whenever possible.

Some people were struck multiple times

and from all kinds of angles.

The Vikings spread out from Scandinavia,

colonizing vast expanses of Europe

from the eighth through 11th centuries.

They are so admired as fighters

that people to this day re-enact their battles.

In Viking times, most men fought with axes and spears.

But those who could afford it used swords for close combat.

The Ulfberht's combination

of strength, lightness and flexibility was an advantage.

The swords were far better than any other swords made

before or since in Europe.

And these must have been extraordinarily valuable

to their contemporaries because of their properties.

Thousands of Viking swords have been found,

most discovered in rivers or excavated from Viking burials

across Scandinavia and Northern Europe.

But only 171 have been identified as Ulfberhts.

The swords as they are today,

it's very hard to see that this was actually

a state-of-the-art weapon.

Buried for centuries,

only corroded skeletons of the once glorious blades remain.

They don't look very much today, but in their time

the Ulfberht was the weapon of the upper strata.

You would certainly notice a person

carrying a weapon like this.

This would be a very precious, very beautiful object,

and a deadly one too, obviously.

The secret of the Ulfberht's construction

has been lost for nearly a thousand years.

But can a modern-day blacksmith recapture that technology

and bring this remarkable sword back to life?

To do it right,

it is the most complicated thing I know how to make

and it's that challenge that drives me.

I don't need a sword, but I have to make them.

Not because I can't do anything else,

but because I can't do anything else.

In northern Wisconsin,

Ric Furrer is starting out on the task of a lifetime.

He's one of the few people on the planet who has the skills

to unravel the mystery of how the Ulfberht was made.

I'm drawing a full-scale paper model

of the sword blade that I'm going to try to recreate.

This Ulfberht inlaid sword was popular

about a thousand years ago

and nobody has made a recreation

metallurgically accurate since then.

I hope to figure out if I can recreate accurately

how these blades would have been made back then.

There are mysteries about everything

related to the making of the Ulfberht.

These were, to a large extent, secrets.

You didn't want to give away

your manufacturing technology for your weaponry

to anybody else.

So we have to look at the artifact

and then reverse-engineer.

Sometimes it's a matter of removing 1/32 of an inch here

or adding it there or...

subtleties that you don't think matter

that can in fact make a huge difference

in how the blade performs.

The trick is to piece together

from enough archaeological evidence to figure out

what the proportions of these blades should be

and then the chemistry.

What is the material that these were made out of?

And that is new information,

why they're metallurgically different.

In London, one of the world's leading experts

on historic steel weaponry, Alan Williams,

recently made a discovery about the Ulfberht

that shocked scientists and sword makers alike.

I've been fascinated by armor and swords

for a very long time

and have always wanted to find out

what they were made of and how they were made.

Smelted iron was the source for swords, weapons, armor

for thousands of years.

From about 800 B.C. till today,

humans have made weapons from steel.

The process starts with iron,

which is found in the ground as ore.

The crushed ore is heated to separate the iron from the rock.

But on its own, iron is too soft to yield a strong weapon.

The trick is to add carbon, most commonly from coal or charcoal.

This hardens the metal and turns it into steel.

But not all steels are created equal.

First, Williams examines a sample encased in acrylic

from a typical Viking Age sword.

Not only does it have low carbon,

it has impurities, known as slag, that weaken it further.

Medieval iron is both soft and brittle.

This is a sample of a sword of modest quality.

These long inclusions, perhaps looking a bit like sausages,

these are inclusions of slag, the non-metallic part of the ore

which has never been separated from the iron.

The slag makes the iron brittle,

which doesn't actually give you a terribly good sword.

Medieval blacksmiths in Europe didn't make slag-free steel

because their fires weren't hot enough

to fully liquefy the iron.

In modern times, metals are melted

at temperatures over 3,000 degrees.

This separates out the slag

and allows more carbon to be mixed in evenly.

But in the Viking era,

carbon could only be introduced incidentally,

mainly through the coal in the fire,

and the only way to remove the slag from the metal

was to try to hammer out the impurities with each strike.

Of the thousands of European swords

from the Middle Ages that have been found,

all were thought to have been made from this inferior steel

until Williams analyzed the Ulfberht.

One or two swords I looked at seemed to be different.

They were made of steel

which I'd never seen before or since in a medieval object.

This seems to be a completely different material.

The first thing that strikes you is that

there are none of these long, grey slag inclusions

which make the metal brittle.

The uniformity is more like a modern steel

than it is a medieval one.

And it has got a carbon content of about three times as much

as the medieval steel we looked at a moment ago.

I thought it was very odd.

I couldn't think of a reason for it.

The only swords Williams found

that were made of this clean, high-carbon steel

were those marked as Ulfberht.

The metal, known as crucible steel,