One way to support the idea is by looking at the power structures. Voldemort's rise to power and his attempts to control the wizarding world can be compared to Hitler's in WW2. But to refute it, we have to remember that 'Harry Potter' is a story of a young wizard's journey, his growth at Hogwarts, his friendships, and his discovery of his own powers. These are elements that are very specific to the fantasy genre and not related to a WW2 plot.
To support it, one can look at the overarching themes. The fight against Voldemort has an aspect of a resistance movement, much like the resistance against the Nazis. The Death Eaters' discriminatory views mirror the bigotry of the Nazis. However, to refute it, consider that 'Harry Potter' is set in a magical world with things like magic wands, potions, and magical creatures that have no relation to WW2.
Supporting the statement, we can note that in both there is a clear divide between the 'good side' and the 'evil side'. In WW2, it was the Allies vs. the Axis, and in 'Harry Potter' it's the Order of the Phoenix and friends vs. Voldemort and the Death Eaters. But on the other hand, refuting it, the 'Harry Potter' series is full of magical elements that are completely different from the historical and technological context of WW2.
To refute it, we need to consider the fact that Harry Potter has its own independent mythology. It has different races like wizards, muggles, and magical creatures. There are no elements from the story of Jesus. It has its own set of values like loyalty, bravery which are not related to religious fanfiction about Jesus.
By simply looking at the facts. 'Harry Potter' was published years before SCP even existed. So it can't be a fanfiction of something that didn't exist yet.
It can be refuted by looking at the origin. Harry Potter was created by J.K. Rowling's imagination. There's no basis in Greek primordial elements for the core concepts of Hogwarts, the sorting hat, or the magic wands. It's a completely different fictional universe.
Yes. There are some similarities. For example, the fight against Voldemort can be seen as a parallel to the fight against the Nazis in WW2. The Death Eaters' ideology of pure - blood supremacy is like the Nazis' ideas of racial superiority. Also, the Order of the Phoenix, which is fighting for good, is like the Allied forces in WW2.
Harry's magic would be a game - changer. He could use Apparition to quickly move around the battlefield and surprise the enemy. His ability to communicate with snakes (Parseltongue) might also be used to gather intelligence if there were any snake - related codes or secrets in the Axis powers. Plus, his experience in fighting dark wizards like Voldemort would give him the strategic edge in combat against the Axis leaders.
Because it is extremely vulgar and goes against the positive and magical essence of the Harry Potter universe. Harry Potter is about wonder, adventure, and good over evil, not this kind of repulsive content.
The 'Harry Potter WW1 fanfiction' re - imagines the wizarding world by showing how magic could have been used during the war. It could be that certain spells were developed specifically for the war effort. The social structure within the wizarding world might also be different. For example, families that were previously on the fringes might come to the forefront if they have special skills or knowledge related to the war. And the way magic is taught at Hogwarts could be altered. There might be more emphasis on defensive magic and spells that can be used to help in a large - scale conflict like WW1.
Ensure the conflict is well - defined. In the original Harry Potter books, there was always a clear threat, like Voldemort. In fanfiction, the conflict should be equally engaging. Maybe it's a new dark wizard or a different kind of magical danger. Also, the resolution of the conflict should be logical. It can't be something too far - fetched or too easy. If the characters face a seemingly impossible situation, they should overcome it through their skills, wits, and the help of their friends, just like in the original series.
There are some 'Harry Potter WW2 Fanfiction' that focus on characters from the original series being transported back in time to WW2. Imagine Harry Potter himself ending up in the middle of the Blitz in London during WW2. He could use his magic to save Muggles from the bombings while also trying to find a way back to his own time. Or perhaps Hermione uses her vast knowledge to assist the resistance against the Nazis, with a magical twist of course.
One interesting 'Harry Potter WW1 fanfiction' could be where the magical world has to deal with the chaos of WW1 on the sidelines. For example, Hogwarts might be used as a secret base to heal wounded Muggle soldiers without their knowledge of magic. Another could involve Death Eaters trying to take advantage of the war in the Muggle world to further their own dark agendas in the wizarding world.