In 1940, the Germans launched one of history's most dynamic invasions,
unleashing a lightning war that simply overwhelmed Allied forces.
This is the story of that invasion,
and of how a small British force, fighting near the French town of Arras, almost threw it off course.
The First World War left deep scars on France.
A third of young Frenchmen had been killed or crippled. Huge tracts of French territory had been devastated.
Frenchmen were determined never to be invaded again.
In 1930, they had begun work on a fortified barrier, named after the then War Minister, Andre Maginot.
This fort, with its barbed wire and steel, has changed very little.
A line of forts like this covered 90 miles of the most vulnerable area of the Franco-German border.
But they stopped short at the frontier with Belgium, France's ally.
These Maginot Line forts
were the cutting edge of 1930s' technology.
They had underground barracks, hospitals and even electric railways.
They were equipped for a variety of threats.
This is a twin 8mm machine gun to deal with infantry.
If tanks appeared,
this 37mm anti-tank gun could be swung forward on a rail, through this armoured shutter.
The Press called this the shield of France.
But a shield can be moved. This steel and concrete can't.
By 1940, war had moved on and made this increasingly irrelevant.
The Germans had used new tactics in Poland the year before.
They brought tanks and close-support aircraft together on the battlefield in a new form of war.
It was called Blitzkrieg.
On May 10th 1940, Germany invaded Holland and Belgium.
The Allies sent the best of their forces to intercept them,
thinking this was the main German attack.
It wasn't.
The Germans had a more daring plan.
They would attack the weak link between the main Allied army and the Maginot Line,
by going through the Ardennes Forest and across the River Meuse at Sedan.
The French regarded the Ardennes as virtually impassable,
so the attack would be a surprise.
General Guderian's three Panzer divisions attacked Sedan on 13th May.
2,000 of Guderian's vehicles were stacked up on this road, waiting to cross.
German aircraft and artillery had pounded French defences all day.
It was the heaviest concentration of air power ever.
MUSIC: "Carmina Burana" by Orff
As German aircraft bombed the French,
tanks, artillery and anti-tank guns, firing from across the Meuse,
pounded the concrete bunkers housing the defenders of Sedan.
The 88mm gun did this damage.
It was an anti-aircraft gun but was used very effectively against bunkers and tanks.
At 3pm, the barrage lifted, and Colonel Balck's First Rifle Regiment crossed the river in assault boats.
French bunkers were back from the water,
so the Germans secured a bridgehead quite easily.
But the French had blown up all the bridges, so the Germans couldn't get tanks over until they built new ones.
The engineers set to work, building bridges under heavy fire,
allowing German tanks and infantry to cross the river within hours.
The defenders of Sedan found the odds stacked against them.
This bunker is pretty rudimentary compared with the Maginot Line.
In 1940, it wasn't even finished.
As nobody expected the Germans to come this way, these positions were held by over-age reservists.
Despite dive-bombing and shelling, the men here fought till German infantry burst in.
Then the little garrison of ten men
was taken out and shot.
At the heart of Sedan is one of the largest castles in Europe,
but medieval stone was no defence against three Panzer divisions.
This part of the town fell easily.
For the third time in 70 years, the Germans had taken Sedan.
Jacques Rousseau has lived in the town all his life.
On 15th May, two days after the Sedan crossing,
the German advance was taking shape.
First, the motorcycle reconnaissance, then the tanks, and miles behind, marching to catch up, the infantry,
still well on the other side of the Meuse.
In the village of La Horgne,
this 20th-century armoured advance bumped into something out of the Napoleonic Wars.
La Horgne was held by two regiments of spahi -
French North-African cavalry.
They had horses,
carried sabres, carbines and had a few anti-tank guns.
They held the village in a desperate day's fighting.
Colonel Balck, one of the German commanders, considered it one of the hardest day's fighting of his career.
The spahi lost 610 men,
including both regimental commanders killed.
These Moroccan and Algerian troopers lie in French soil.
It's a cruel irony that their sons may have fought for independence AGAINST France only ten years on.
The biggest danger to the Germans
was that the Allies would get between their armour, forging ahead,
and the infantry miles behind.
Guderian had already been in trouble with his superiors for moving too fast.
On 17th May, here at Montcornet,
a few dozen French tanks under Colonel de Gaulle jabbed into the flank of the German line of advance.
They shot up German trucks before they ran out of momentum and petrol.
It was an indication of how vulnerable the Germans were
and of what might have been achieved, had the Allied commanders been able to mount a co-ordinated attack.
Once they reached these straight roads across northern France, the Germans fairly clipped along.
Almost nothing was in their way.
Captain von Kielmansegg of First Panzer Division described that odd vacuum behind the Panzer divisions -
"In this peaceful landscape, human beings are absent.
"Everything is dead and empty. Not even the old people have remained."
The German plan was working brilliantly.
Blitzkrieg was as much about psychology as about fighting.
The Panzers were moving so fast that the Allies were stunned,
unable to react effectively.
By the time they planned a counterattack,
the Germans were halfway to the Channel.
But most of the Allied army was still in Belgium.
At last, amid hesitation and misunderstanding,
a small British force was sent to counterattack the Germans at Arras.
Arras had been ruined in the First World War.
Re-building was barely complete
when, in May 1940, it was bombed.
SOPRANO SINGS LIEDER
German dive bombers -
a terrifying part of the campaign - set fire to parts of the town.
This World War One memorial was hit by bombs that destroyed the station.
There was only a tiny British garrison here. Most of the British Army was in the north, in Belgium.
The British Army had been in France since September 1939, but few of its men had seen any action.
Britain's main tank was the Matilda.
It was slow-moving, as it was made to be used with infantry.
But most of the infantry hadn't seen a tank, let alone trained with one.
This is one of the few surviving specimens of the infantry tank, Mark One, known as the Matilda.
It lives in the tank museum at Bovington.
It's cramped, slow, poorly armed but heavily armoured.
Not the ideal thing in which to take on a Panzer division.
Peter Vaux fought at Arras and remembers all too well the shortcomings of the Matilda.
What's it like seeing one of these?
I never thought I'd see one again.
We had 58 at Arras, and we left most behind.
It was produced in 1938 to a budget of £11,000.
The requirement was to have a slow-moving tank. God knows it was, at 8mph!
It was to be thickly armoured.
You have a look at the thickness of this. You've got 60mm there...
and on there and the turret... Even more in places.
- Two-man crew? - A commander up there and a driver down here.
The commander was very busy.
He had to command his tank and fire that gun.
It was a difficult gun to fire.
He had to operate the radio at the back.
To turn the knobs on it,
he had to lie on his stomach with his feet at the driver's back.
That was very hard to do in battle.
- This running gear looks very exposed. - All this, very vulnerable indeed.
I saw one tank in the battle
that had had this suspension unit completely blown off.
And yet it was hobbling along.
Of course, if this was broken, the tank was crippled.
Here we have the engine.
A straightforward Ford V8 engine from a car.
It constantly broke down.
That was the big weakness. To mend it, you had to open these things, which was difficult under fire.
- So, well-armoured, poorly armed... - Well-armoured.
Stupidly armed with one machine gun.
But their anti-tank guns couldn't do US any harm in this, either.
Only the big guns blew us to pieces.
German officers since have told me
that they were amazed at how their anti-tank shells bounced off this.
Troops and tanks going to Arras had a hellish journey from Belgium,
on roads made perilous by German dive bombers.
The roads were choked...
with Belgian and French refugees crossing northern France,
fleeing the German advance.
The British were to rendezvous at Vimy Ridge, just north of Arras.
Most arrived exhausted and ill-prepared for the battle.
I'm up on Vimy Ridge, amid trenches that date from the First World War.
These trees were to commemorate Canadians lost during the war.
Many died capturing the ridge in 1917.
Some of the British who fought at Arras in 1940
got some sleep here the night before the battle.
It must have been eerie, on the eve of their first battle,
for them to spend the night in First World War trenches.
A British tank officer tells us what it was like -
"I arrived at Petit Vimy exhausted and disorganised.
"I was given a map by my commander and told to follow him.
"The wireless didn't work. There was no tie-up with infantry and no clear orders.
"This was our state as we crossed the start line for our first action.
"It wasn't a very auspicious start."
# We're gonna hang out the washing on the Siegfried Line
# Have you any dirty washing, mother dear?
# We're gonna hang out the washing on the Siegfried Line
# Cos the washing day is here
# Whether the weather may be wet or fine
# We'll just ramble on without a care
# We're gonna hang out the... #
This abbey in the shadow of Vimy Ridge was ruined in World War One.
On 20th May 1940, the Twelfth Lancers, a British reconnaissance regiment, was here.
The Lancers reported that the Germans had passed along that road
and that the area was stiff with German tanks, infantry and artillery.
But the men had been told to attack the Germans in the Arras area
and had been given the impression that there were very few of them.
In fact, the British were throwing a handful of tanks and infantry into this whirlpool of German armour.
The attackers left Vimy Ridge late on the morning of 21st May.
Their plan was simple enough.
There were two columns.
Each consisted of 40 tanks of the Royal Tank Regiment,
Durham Light Infantry and some motorcycle reconnaissance.
They planned to go round Arras and not meet any Germans until they were south-west of it.
It was hot, and the tanks got ahead of the infantry, who were marching, heavily laden, down this road.
The sight of a First World War cemetery can't have been encouraging.
The Durham Light Infantry in the right-hand column
had fought a small battle and got separated from its tanks
by the time it reached Warlus.
Its leading company pushed on down this road but soon ran into heavy opposition and had to fall back.
It's typical of the day's confusion that it was just short of the line where the battle was meant to start.
SOPRANO SINGS LIEDER
Some of the Durhams gathered by this water tower outside the village,
where they were attacked by dive bombers.
One of them remembered... "We were subjected to a terrifying aerial attack. Everybody was shattered.
"After a few minutes, the officers and NCOs collected themselves and said, 'We must get on with it.'
"It was hard to get some men moving. We had to kick them into position, and the effect was considerable."
The Durhams fell back into Warlus. Later that night, they broke out with the help of French tanks.
The survivors were back up on Vimy Ridge by six the next morning.
The two columns of tanks,
both moving well ahead of their infantry,
ran straight into Seventh Panzer Division.
Its commander was a little-known major general who was soon to spring to prominence in North Africa.
His name was Erwin Rommel.
Late in the afternoon, Rommel arrived in the village of Vailly to find chaos and confusion.
He drove up onto this hillock, where there were some German guns,
only to be attacked by British tanks coming from Arras in the north
and from the west, across the main road.
Rommel galvanised the defence
with the help of his aide-de-camp, Lieutenant Most.
"With the enemy tanks so close, only rapid fire from every gun could save the situation.
"All I cared about was to halt the enemy tanks by heavy gunfire.
"The worst seemed to be over, when suddenly Most sank to the ground behind a 20mm anti-aircraft gun.
"He was mortally wounded, and blood gushed from his mouth."
Rommel's personal intervention had checked the attack here,
but the British had come within an ace of killing a general who was later to cause them infinite trouble.
The left-hand column, curling round the suburban fringes of Arras, did better.
Its tanks, moving ahead of the infantry, got as far as the level crossing which stood here,
and found it down.
Old habits of peacetime die hard,
and it took some time before an officer summoned up the nerve to crash straight through.
Just over the other side, the tanks ran squarely into a column of German infantry in trucks.
The Germans had nothing to penetrate the armour of British tanks, and dozens were killed or captured.
One British officer said we had a glorious free-for-all...
"I didn't see why we shouldn't go all the way to Berlin."
The British didn't get to Berlin.
They got barely another two miles and were stopped here by field guns firing from that ridge.
One officer drove up here and saw 20 tanks lying in this field,
their crews dead beside them or crawling through the grass.
He gunned the wood and saw artillery observers fall out of the trees.
He passed his commanding officer's tank with its side blown in.
He wrote, "Although I didn't know it, the Colonel and his radio operator were dead inside it.
"This was the high watermark of British success."
The battle was over.
As night fell, the survivors tried to get back to Vimy Ridge.
But the area was full of Germans, and many British were taken prisoner.
The Royal Tank Regiment lost half its tanks, and nearly half the infantry were killed or wounded.
But the battle shook the Germans.
Rommel reported that he'd been attacked by five divisions.
In reality, the total British strength was less than one.
I'm back up on Vimy Ridge with the First World War memorial behind me.
Most survivors of the Arras battle also ended up here at the end of the day
and were evacuated from Dunkirk.
In simple terms, their attack had failed.
But it sent ripples of alarm throughout the German High Command.
The German commander, von Rundstedt, was seriously worried...
"A critical moment came as my forces had reached the Channel.
"It was caused by a British counter-stroke south of Arras.
"It was feared that the Panzers would be cut off before the infantry had arrived to support them.
"No French counterattacks carried a serious threat like this."
This mood contributed to von Rundstedt's decision to order his armour to halt.
German tanks remained stationary for several crucial days.
This gave the British the chance to mount an evacuation from Dunkirk.
Nearly 340,000 soldiers were taken to safety.
Dunkirk was something of a miracle.
The difficult process of evacuating so many thousands took days.
The last troops were taken to safety on June 4th,
leaving the beach strewn with wreckage.
The Channel was Britain's shield against defeat.
It was four long years before British troops returned in strength.
The German invasion had been an extraordinary success.
Some Panzers had fought their way from Sedan to the coast in seven days - a journey of over 200 miles.
Yet the Arras attack proved that the Germans were not invincible and that their offensive had entailed risks.
But it was the Allies' tragedy that, mesmerised by Blitzkrieg,
they never managed to turn these risks to their advantage.