Well, this is quite entertaining, eh what? Now, this particular one here is more of a scene-setting prologue piece, more a statement of an idea rather than a story. Someone once said that Harry Potter was the "little black dress" of fanfic because it dovetails so well with everything.

Anyway, here's a milieu someone might like to consider...

Vault 9¾

Onceit had been known as Dufftown, Whisky Capital of the World. Now it was rubble. South of it had been Pole Forest. Now it was barren. Those trees that hadn't been harvested for the war effort had been felled by nuclear fire, or the black rain that had followed.

South of the town, beneath what had been a distillery, the hideous screeching of tons of metal sliding against tons of metal echoed in a skeleton-filled antechamber. The giant cog-shaped door slid out of its frame before rolling with great clashing sounds to one side.

"They'll be on us in no time!" The voice was pained, but the echoes made it difficult to determine the speaker's gender. "Get through the door! Quick!"

Now life entered the chamber, scattering bones, ancient signs of desperate entreaty, and old cans: three children, ranging in age from eleven to fifteen, all wearing blue jumpsuits with yellow trim. Vault-Tec standard for Vault 415.

The man who staggered through after them was a contrast. His garments were robes, apparently homespun, dirty, and now holed. He raised a small stick back the way he came, muttering words that caused flashes of red to reply to the sounds of shouts and gunshots inside.

One of the children screamed as a bullet smashed a skeleton by her feet. The eldest cottoned on quickly, grabbing the others and pulling them to one side. The man in the robes also half-fell aside, grappling with a rusted control panel and setting the great door in motion.

"Sir! They've escaped!" could be heard over the cacophony of the warning siren and crashing of the door.

"Not if I can help it," another voice, this one angry, "I'll speak with the Overseer and..."

A scream of sliding metal cut him off.

The robed man leaned against the panel, breathing hard for a bit, before straightening up and looking himself over. He then aimed his stick at his midsection and muttered something like "episkey", bathing the area in light before he turned to check the new-found wizards.

"You're not injured? Any of you?" Three young faces, blank with shock, stared back.

"Well then," the man declared, pulling a piece of rope out of a pocket, "We need to get you to safety. Um..." He scratched the back of his head and looked embarrassed. "I really should have done this before, but with all those guards shooting first and asking questions later, I, ah, forgot. Anyway, everyone grab hold of this and off we go!"

Naturally the children just gaped at him. One was beginning to shake, and the eldest was looking mutinous.

"You can't go back, they'll probably kill you," he added, a little curtly, "and you can't stay here, and I'm not leaving you here either. Hold onto the rope," he extended his hand, the unremarkable looking rope dangling from it, "and I'll make sure you get to safety."

"Where?" the eldest was definitely going to be a problem.

"I'll tell you if you take hold of the rope," the man said, starting to sound impatient. "Deal?"

The three children looked at each other, then the eldest stepped forward and grasped the other end. The other two stretched their arms to gingerly hold it as well while staying as far away from the strange man, who had turned their lives upside down, as they could.

"We're going to Hogwarts," the man said before they all vanished, leaving nothing for the Vault guards, when they finally emerged in full hazard suits and assault weaponry, to trace.

As the Muggles entered the first years of what was then known as the Resource Wars, they quickly became aware of our lands – lands not charted on their maps, and which they could not enter, but that could be plotted by noting where investigators ceased to progress – namely, the boundaries of the wards. Desperate to maintain the Statutes of Secrecy, the Ministries of the various wizarding countries began to resort to sometimes extreme measures. Thus the Secrecy Wars began, and frankly, served to poison Muggles against us, when we should have realised the jig was up.

– Mungavin Dobbsley, The End of the World and How it Happened

Andrew Harris had by now spent seven years at Hogwarts Academy of Witchcraft and Wizardry, being taught as much as they still knew about the arts of magic. Seven years since he, Lynda and Carl had been chased out of the Vault they once called home, chivvied along by a man who had done things that were scientifically impossible. Things he could do now.

He still had trouble comprehending that some kink in his DNA allowed him to flaunt reality with impunity, fly on a broomstick, and create useful potions from ingredients that common sense told him shouldn't even exist let alone be safe to consume. In that respect the younger children had it slightly better, but wizards these days weren't able to be picky if they wanted to survive as a race.

His acromantula silk robes whispered about him as he climbed the spiral staircase to the Headmaster's office. The stairs had once moved, but the devastating energies of the war had wrecked whatever spells animated them. Nobody had ever managed to make them work since.

"Come in," Severus Potter responded to Andrew's knock.

The old wizard, beard quite short by pre-war standards, was sitting at his desk looking out the window. Once stately lawns and ornamental garden beds were long gone, replaced by orderly rows of food and potion crops. While serviceable, Severus couldn't help but think that some less utilitarian plantings would look nice and increase morale.

"Headmaster," Andrew nodded to the wizard.

"Master Harris," and Severus nodded to a chair, "I think you'll want to sit down."

Andrew took a seat and frowned. If the Headmaster was urging him to sit, it was probably bad news.

"You see this?" A finger indicated the inexplicable device on his desk. It seemed to be a set of disparate parts that glowed slightly.

Andrew did. "Yes sir?"

Severus smiled faintly. "I take it you've heard of the legend of Vault 9¾?"

"Um... yes... sir?"

"Such a place exists."

Andrew just stared at the wizard and seriously considered whether or not the Headmaster had gone mad. His history teachers had all asserted that if there had been such a magical sanctuary, named in the same way as the Muggle Vaults, it was probably buried under rubble, or otherwise lost forever, and certainly wouldn't live up to the wild tales spread about it.

"I'm sure you've seen the great doors to the dungeons," Severus was speaking and Andrew blinked himself into attention, "But being as they're now permanently open, you wouldn't have seen the number 21½ on their forward faces. Yes, young man, we created our own Vaults, just like we had our own government, our own railway line between here and London.

"This device is a beacon, and it is a beacon for," the old wizard's fingers rotated the device to show the legend Vault 9¾ on the base, "well, you can see for yourself. We took it to the southern boundary of our lands here, and saw its light brighten. Since London in general, and Diagon Alley in particular, is south..."

"It gets brighter as we approach!" Andrew was pleased at the Headmaster's nod.

"Exactly. Vault 9¾ was to be a storehouse of wizarding knowledge, and more importantly, of magical life. As long as this device glows, the Vault awaits.

"I believe you would be an ideal candidate to join the quest for it."

Well, I think we all know where this goes. About 2277, a ragtag bunch of young wizards follows what's left of the rails of the Hogwarts line down the length of Great Britain into King's Cross, seeking the treasures of Vault 9¾. Along the way they discover the remains of several magical communities, mutants, homicidal scavengers, equally genocidal Muggle communities, and just how well the Goblins have fared.

In this version of the universe, the Resource Wars exposed the wizarding world for obvious reasons, and the wizards' response to this was... how shall we say this... disastrous. While some Muggles and wizards have made their peace, most others haven't. Add to that the machinations of Vault-Tec, the descendants of Chinese fifth columnists, and the British ruling class, and the scene is set for possibly changing the world for the better.

Possibly.

Obviously we're talking about mostly the Fallout world, but this is an area most fanfiction writers don't consider: What else happened elsewhere? The world's bigger than two ends of the USA after all.