Its one of the longest running debates on the internet. Quite simply, who would win - muggles vs wizards?
I've had FB conversations running into the hundreds of comments on this topic, with opinion typically divided about 50:50. Some are adamant that the wizards would 'obviously' win, while others, including myself, caution that in the long-term the Muggles would likely dominate.
Part of the reason this debate goes on so long is that it hasn't ever really been depicted in fiction. We haven't seen a film or book about it (though admittedly I'd love to try writing some fanfiction along those lines someday). However, there are other proxies in media we can draw upon as supporting evidence.
X-Men Days of Future Past came out a few weeks ago, and depicts a scenario quite similar to a hypothetical Muggles vs wizards war (spoiler alert). In the near future, mutants have been hunted down to the brink of extinction. One must immediately wonder - how did this happen? With members of their kind having the ability to shoot fire, control people's minds, teleport, transform their bodies, telekinetically control metal or the weather, phase through walls, heal from almost any injury, and so on, what could possibly defeat them?
There is an answer however -
Despite their powers, the mutants are badly outmatched by the 'Sentinels' - a class of newly built machines designed to detect and kill mutants. Relentless, all-but numberless and very hard to destroy, before long the mutants can only keep running. Ultimately there is nowhere to hide.
We see in the film how the various superpowers the mutants have prove ineffective against the Sentinels. Flames that would easily boil a human alive hardly bother them, while freezing them will only keep them are bay temporarily. They can't be mind controlled, confused or otherwise attacked telepathically. Even Magneto struggles against them, as they are made of a composite material without any metals. Here's a clip here -
While admittedly the technology required to build them is said to involve 'tissue samples taken from Mystique' so that they can rapidly adapt their bodies to new conditions, we can assume this is just a handy plot device. There's no reason to believe that advanced machines of this nature aren't just around the corner in real life. They're essentially terminators after all, and given how quickly robotics and drone technology are advancing, its not hard to believe we'll be able to build similar creations within a few decades.
The point I am making is this - most of the superpowers and special abilities you see among the X-Men have strong parallels in Harry Potter. Sentinel-like machines would be immune to most curses. They couldn't be imperiused, or tortured with the cruciatos curse, while Avada Kedavra would presumably be useless. Like inferi, they don't bleed, rendering Sectumsempra ineffective. You couldn't perform memory or confundus charms on them, or any of the other little tricks wizards use to hide from Muggles.
Sure there are some spells the wizards could still use. Wingardium Leviosa could perhaps be used to levitate them away, while violent curses like Confringo or Reducto could still blast them apart, but how many times will that be good for? A skilled wizard could take out a few, but given our advanced industrial society, we could surely make many millions of them. Almost half a million tanks were built by the warring sides in WW2 for instance, and that was back in the 1940s. Some 60 million cars are now built every year, and in a wartime situation that number could be multiplied quite a few times over.
The exact demographics of the wizarding world are somewhat in dispute, but the wizards appear to consist of somewhere between 1 in 1,000 and 1 in 10,000 people worldwide. This comes to a total population of around 1-5 million. It seems we could easily build a hundred Sentinels, or even a thousand, for every wizard alive within a few short years.
Looking at some elements of the wider debate, and thinking it through logically, most wizarding defenses could be penetrated one way or another. An invisibility cloak might hide you (presuming it blocks all forms of radiation, including infrared) but it doesn't omit sound. A person's footsteps, or even their heartbeat, would give them away instantly to a sensitive microphone, with which the Sentinels would surely be equipped.
Alternatively, a wizard could perhaps conjure up a box around themselves, and perform an unbreakable charm on it. Assuming that 'unbreakable' is meant literally (i.e. you could drop a nuke on it, or fling it into a black hole, and it still wouldn't break) this doesn't meant that the contents on the box would still be safe. Try picking up the box and dropping it from a tall cliff. The box may not break - but the people inside will.
A demonstration of precisely this occurs in the movie The Incredibles. Superpowered Violet is able to project shields around herself. These easily stop bullets and other small objects, but at one point Syndrome's Robot - which clearly weighs many hundreds of tonnes, flings itself down on top of her, knocking her down and almost killing her when she crashes against her own shield.
It also says nowhere that an unbreakable barrier doesn't permit heat to pass through it for instance, or other forms of radiation. Try lighting a fire under the wizard's unbreakable hidey-hole, or target a laser on it, to boil them alive inside. A flame-freezing charm might avert this, but one wonders how powerful such charms really are. There are obvious limits to magic. A wizard can easily levitate a feather, but not a mountain. They can presumably survive a fire, which burns at around 1,000C, but could they survive a nuclear explosion, where the temperature can get into the millions of degrees?
Wizards can also apparate, giving them a very handy method of escape, but one wonders exactly how many times it could be used. Eventually even wizards have to sleep, and it only requires one mistake out of a thousand to let the Sentinels catch you. Then there is the question of how you'd be alerted to their presence in the first place. Accurate guns can target an enemy kilometers away, before they even know you're there. Check out this video of an American helicopter attacking insurgents in Iraq for instance. Its hovering in the dark miles away before it opens fire. How does a wizard deflect a bullet they can't even hear coming? (fast forward to 2 minutes in)
One further point would be the question of how the Muggles would even find the wizards in the first place. Refuges like Hogwarts and Diagon Alley have presumably gone undetected for centuries. There are likely ways around this however. It is repeatedly said that electronics don't work around Hogwarts. This would actually seem to be quite a vulnerability however. This means that, like sending a canary down a coal mine, an inexplicably malfunctioning machine would be a sure sign of magic nearby. There are said to be further charms on Hogwarts to ward off muggles - including making the castle look like an old ruin, making intruders forget why they are there, or alternatively causing them to suddenly remember urgent appointments and compel them to leave.
These would seem fairly weak in the face of the modern world however. It might have been enough to prevent the odd peasant from wondering onto Hogwarts' grounds back in the Middle Ages, but how does it affect aerial or satellite surveillance? Here's what you do - spot the ruin, send in a few scouts, and if they come back looking somewhat bamboozled (as if by magic) try dropping a nuclear bomb on it.
There's also the unmistable genetic trace of wizarding blood. The way it's depicted in the books, the ability to use magic is obviously a recessive gene, one passed down through the generations. The Harry Potter books occur in the 1990s, which is before the completion of the Human Genome Project in 2003. As of 2014 it should have been possible by now, or would be soon, to detect these genes through routine DNA tests. Indeed - this same mechanism is used by the sentinels to detect mutants, as well as people who might one day give birth to mutants. X-Men again delivers.
Now there are some possible methods of the wizards causing mass death and destruction among the Muggle populace that I've seen suggested. They could infiltrate the Whitehouse and the Kremlin, imperiuse a number of world leaders, and spark a nuclear war killing billions. Even this wouldn't be an end-all however. The world's nuclear arsenals have been steadily shrinking for decades, and even a successful strike would only kill a large chunk of the world's population. Muggles would still outnumber wizards by a hundred or thousand to one. Hell even if only New Zealand survived - with its four million people, the wizards would still be outnumbered.
There are other suggestions, like putting large batches of sleeping potion in the water supply, or broadcasting a TV image of a Basilisk's face. These could certainly kill (or in the latter case - incurably petrify) millions of people, but far from everyone. Many people already get their water supplies from rainwater, and of course not everyone would be watching TV at any given time.
Even major losses like these the Muggles could easily recover from. Our population is exploding at a rate of almost 100 million people a year. We've survived world wars, bubonic plagues, famines, earthquakes, hurricanes...more than a million of us die in traffic accidents alone every year and no one bats an eye.
The bottom line is this - no matter how hard they tried, wizards would be unlikely to ever compete with cancer, malaria, AIDS or heart disease as a leading cause of death among the human population.
There is one possible caveat to all this however, though it is by no means a trump card. The X-Men in Days of Future Past do eventually escape the Sentinels. This is by sending a message back through time to prevent their creation in the first place, which is the real subject of the film. Time travel does exist in the Wizarding World, however J.K Rowling herself has stated that Time Turners can only safely be used to go back a few hours -
There are further problems with this. If wizards can utilize time travel, then why couldn't Muggles? As far as I'm aware, its never been said that a Muggle couldn't use a Time Turner if they stumbled across one. For a wizard to go back a significant time period, i.e. to make more than a tactical difference to their situation, they would risk preventing themselves from ever being born in the first place, making it a case of Mutually Assured Destruction. This is probably the best the wizards could hope for.
Other than that however, in a full-on war against the Muggle world, the wizards probably wouldn't have a hope of winning in the long run. At the rate our population is expanding, and our technology is advancing, we're rapidly leaving them behind. Think Nazi Germany invading the Soviet Union. The German armies were devastating at first, but the Soviet's numberless reserves eventually wore them down. An old quote by Von Clausewitz also comes to mind - 'Never fight the same enermy too long, or he will learn all your tricks...'
Think also of the sorts of technology we'll likely have access to in the near future, everything from interstellar travel and antimatter bombs to being able to upload our consciousness into machines. Before long its no longer a question of Muggles vs Wizards, but every devastating hard sci-fi weapon you've ever heard of...vs a few wizards.
It'd be a slaughter.
To conclude - the wizards can run, but they can't hide.
