December 10, 867 AD — Deep Night
Because of the cold wave, the Little Belt Strait, which normally separated Jutland and Funen with rough waters, had frozen solid.
Under the dim moonlight, the sea had transformed into a vast expanse of hard, gray-white, silent ice stretching all the way to the indistinct opposite shore. Bitter winds howled across the frozen surface, carrying flurries of fine snow.
Then—
Countless pinpricks of fire appeared in the darkness.
Wrapped in thick furs and carrying a dim whale-oil lantern in his right hand, Carloman led more than six thousand Frankish soldiers onto the ice.
The men wore bulky winter clothing and carried packs and weapons as they struggled forward.
The wind cut across the open sea like blades, stinging exposed skin. Every breath emerged as white mist.
The frozen sea was far from smooth.
Some sections were slick as polished stone—one careless step meant a hard fall.
Others were cluttered with jagged ridges of ice that made movement exhausting.
To move supply wagons safely, the Franks spread straw and branches over the slickest areas. Soldiers pushed and hauled together while wagon wheels creaked over shattered ice, the sound echoing unnaturally across the frozen emptiness.
"By Odin… have the Franks gone mad?"
On the coast of Funen, two Viking sentries stared blankly at the thousands of figures slowly crawling across the ice.
The strait had frozen before in years past—
But this was the first time anyone had dared march an army over it.
After standing stunned for a moment, the sentries lit three signal fires and ran toward the military camp two miles away to wake Halfdan.
"The Franks are coming?"
"Heh. Very funny."
Halfdan shoved aside the maid beside him.
He suspected the men had frozen their brains and started hallucinating.
Still wearing a dark expression, he armed himself, threw on a fur cloak, and rode west toward the coast—
Only to freeze in shock at the sight.
"I raided you a few times—is this really necessary?"
Halfdan immediately rode back.
His Viking troops were in chaos.
Men rushed about like frightened sheep.
Many had misplaced weapons and armor and were in no condition to fight.
With no better option—
Halfdan burned the barracks and supplies and led his army northeast.
After weaving around several forested areas, they successfully escaped Frankish pursuit.
Funen could not be held.
Spending a full day retreating, Halfdan reached a northeastern harbor.
Facing panicked crowds, he declared that he and his household guards would remain behind to cover the withdrawal.
He persuaded the soldiers to board ships in order and avoid killing one another fighting for passage.
Watching the first ships depart, Halfdan roared:
"If any of you still have a shred of decency—send the ships back for me!"
Unexpectedly—
The Franks ignored his harbor.
Instead, they marched directly for Odense, the largest settlement on the island.
Then they continued east—
All the way to Funen's eastern shore.
Ahead lay the Great Belt Strait.
Wider than the Little Belt—
But frozen all the same.
One daring Frankish knight mounted a sled and tested the ice first.
The soldiers behind followed on hastily built sleds, slowly crossing toward Zealand.
As they neared shore—
One hundred Viking archers gathered to oppose them.
Arrows shrieked overhead—
But they failed to stop this unprecedented gamble.
"Deus adjuva!"
(God, help us!)
The first twenty Frankish knights to land shouted the cry and drew their swords.
They smashed through the archers with ease.
More Franks landed.
Then continued eastward—
Attempting to repeat the feat and push straight into Sweden.
When news reached Copenhagen, the count there nearly panicked.
After the Second Frankish–Danish War, Zealand had become one of Britannia's overseas territories.
Disaster seemed imminent.
By instinct, the count turned to the military.
"Colonel, what do we do?"
"Call for the Gotland garrison?"
Colonel Hadava shook his head.
"No use."
"Gotland, Bornholm, and Viljanka together only have thirteen hundred troops."
"We'll have to rely on the Nordic coalition."
Patiently, he urged the count to organize defenses.
Copenhagen still possessed a five-meter-high wooden palisade.
It should hold against the Franks.
That afternoon, Halfdan's plea for help reached Copenhagen.
Hadava took his fleet to evacuate the retreating force and transported Halfdan's army to southwestern Sweden, stationing them east of the Øresund Strait.
Compared to the Great and Little Belts—
Øresund almost never froze.
Even the oldest residents had never seen ice thick enough to walk across.
Two days later—
Carloman's army reached eastern Zealand.
To move faster, many exhausted soldiers had been left behind in settlements.
Only five thousand men remained.
Unfortunately for him—
Øresund was still open water.
Carloman attempted to storm Copenhagen.
But the freezing conditions slowed movement, and the Franks failed to break the five-meter palisade.
As time passed—
The cold wave weakened.
Temperatures slowly rose.
Carloman realized crossing the strait was no longer realistic.
He ended the offensive and rested in central Zealand.
More than a month passed.
Øresund never froze.
The coldest season was ending.
The Great and Little Belts could thaw at any moment.
Many nobles urged withdrawal.
"Your Majesty."
"You've achieved something never done before."
"It's time to leave."
"We weren't defeated by Viking barbarians."
"We were defeated by nature."
They weren't wrong.
During the occupation, a hastily assembled Viking coalition of over seven thousand men attempted a counterattack—
Only to be crushed by Frankish knights.
After that defeat, the coalition hid behind Copenhagen's walls while the Franks looted settlements across the islands.
"Withdraw."
Carloman accepted the army's collective judgment.
Before leaving—
He thoroughly plundered both islands and returned to Jutland carrying heaps of stolen goods.
February, 868 AD
When Vig learned that Carloman had withdrawn, his mood improved somewhat.
When the first reports arrived that Frankish forces had crossed both Belt straits—
He had genuinely been alarmed.
The event immediately reminded him of a war in the mid-17th century (1658), when Swedish armies crossed frozen seas and forced Denmark to cede land and pay indemnities.
But in the end—
Carloman had failed to cross Øresund and invade Sweden itself.
Looking back—
It had been a successful tactical operation.
But strategically?
A failure.
He had failed to invade Sweden and Norway and force Vig to divert troops.
"Actually…"
"Carloman overestimated how important the Nordic territories are to me."
"Even if he captured Gothenburg, Oslo, and Uppsala…"
"He still wouldn't force me to recall the expeditionary army."
After a few thoughts, Vig turned his attention back to West Francia.
As long as he destroyed the strongest power on the continent—
The rest would never become a serious threat again.
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