I don't think HP ghosts are tied to their place of death. The Grey Lady (Helena Ravenclaw) was supposedly killed in Albania by the Bloody Baron, upon which she became a ghost and went to Hogwarts.

You have a point regarding their motivation for helping wizards, but I don't think that's such a huge obstacle as to prevent all ghosts from refusing to help. Surely wizards could convince some ghosts to help them out; also, considering Nearly Headless Nick was somehow de-Petrified, there are clearly magics that can affect ghosts. That means there's a possibility that unwilling ghosts could be compelled to do wizards' bidding.

 

ROFL, you mean you thought for a second that it wouldn't?

Where's Lily Potter?

That was my clever way of saying that not all magical folk turn into ghosts upon death, and I doubt you can turn a wizard into a ghost on purpose, or become one by choice. Using the 'unfinished business' excuse would be stretching it.

I should have used different language. Ghosts seem to be tied to one place which was important to them.

That's why the Grey Lady ended up at Hogwarts, even though she died elsewhere. By that token, you could sneak into the Pentagon, kill a wizard, and even if he did end up becoming a ghost, he could very well end up haunting his favorite Knockturn Alley whorehouse. And I still don't think they can move beyond their haunting grounds.

 

Ah, but you forget the Deathday party Nearly Headless Nick had in CoS, where many ghosts who seemed to be from outside Hogwarts showed up to celebrate.

 

"Wizards can leave an imprint of themselves upon the earth, to walk palely where their living selves once trod, but very few wizards choose that path."
Nearly-Headless Nick from OoTP. So presumably if there was a suitably dedicated wizard, they could choose to become a ghost and infiltrate important places. Although that doesn't address the issue of where they're tied to in death...you could perhaps argue that if they were dedicated enough to die in a certain location, they might haunt that location as well.

 

If I were to use magic to infiltrate somewhere as secure as the Pentagon, I'd probably use a portkey followed by invisibility/disillusionment spells or polyjuice potions. I'd also probably place an invisible portrait on the wall or ceiling of each important room and have the portraits themselves spy on everything that happens. I'd then obliviate the person who got the portraits in there, or simply kill him, and have the portraits report solely to a trusted person.

On the other hand I could apparate into the White House and imperius the President. Either idea works.

 

Warlocke's point about the fact that most wizards are useless is entirely accurate.

In a wizard vs. Muggle war, I suspect most of the useless wizards would get culled very quickly (depending on your position on how capable Muggles would be of getting into somewhere like Diagon Alley, or the Ministry of Magic).

However, it also seems to me that it only takes one competent wizard - they don't even have to be someone like Dumbledore, any Auror would be able to do it - to cause a fuck ton of damage. For example, a few well-placed Imperius curses and you've taken out the entire Muggle command infrastructure.

 

Conjure poison gas! Conjure poison gas!

Put poison in the water, and zippidy-do-da away.

 

Even better, curse the water so that it kills everyone who drinks it and reanimates their corpses.

Zombie apocalypses, proven method of destroying muggle civilisation in 1-6 weeks.

 

Idea box part2: following the 'outing' of wizards to muggle society, there is a brief effort by magical officials to represent their position in a way that doesn't seem like magicals are part of an overlord class.

Unfortunately, post-combat interviews with the trio indicate that they expect memories to be modified to cover up this situation. While Scrimgeour and the ICW scramble to cover their asses, a black ops squad takes the first blood against a magical enclave, hoping to gain leverage on the inevitable war with a preemptive strike.

The ICW conference goes up in flames.

Now the devastated wizarding leadership begins to realize that a corner has been turned, and looks for a trained force of strike-capable wizards that might be able to put the fear of magic back in these muggles.

"During these negotiations, I would be willing for you to address me as Lord V."

 

You had me until Lord V. Although I actually do like the idea.

 

Also, now that I think about it, I remember that Myrtle went around haunting Olive Hornby:

So HP ghosts are definitely not tied down to a single place, and there are also magics that can be used to control said ghosts.

 

I did forget, didn't I?
Though one could argue that they were only able to travel because it was Halloween, when the 'veil' between worlds thins (as they say).

Interesting...