He could have found a magical artifact. There are many artifacts in the Harry Potter world that have strange and powerful abilities. It could be that this artifact has the power to create clones. He figures out how to use it, perhaps with the help of Hermione who is good at researching such things. And then he starts creating his clone army.
Perhaps Harry Potter is forced into a situation where he has no other choice but to create a clone army. He might be facing an extremely powerful enemy that he can't defeat with his normal abilities. So, he delves deep into his magical knowledge and experimentation. He might combine different spells and potions in a way that no one has ever thought of before, and through trial and error, he manages to create a clone army.
Definitely Hermione. Her intelligence and vast knowledge of magic would be a great asset if cloned. She could help solve complex magical problems and come up with strategies in battles.
It could also change his relationships. His friends might be worried about this new and rather extreme power he has. They might question his motives and whether this is the right way to deal with the problems in the wizarding world. On the other hand, his enemies would definitely be more cautious around him.
In the 'Harry Potter makes a clone army fanfiction', perhaps Harry creates the clone army to protect Hogwarts. He might use some ancient magic spells he discovers in the library. These clones could be modeled after the greatest wizards in history, like Merlin. They would bring a whole new level of defense to the school against the dark forces.
In this fanfiction, Harry might also include some of the Hogwarts ghosts in his army. After all, they have a long - standing relationship with the school. Peeves, for example, could be a wild card in the army. He can cause chaos among the enemies. And some of the older students who have a strong sense of justice, like Cedric Diggory's friends, could also be part of it.
He might face opposition from the school authorities or other wizarding institutions. They could see his army - building as a threat. Also, finding resources to train and equip the army could be difficult. Magic items and training grounds are not easy to come by. And he has to keep the existence of the army a secret from the Death Eaters, which adds another layer of difficulty.
Magic can provide unique advantages to the British Army in fanfiction. Spells like 'Protego' can be used to create shields for soldiers during combat, protecting them from bullets and other weapons. Wizards could also use 'Apparition' to quickly transport troops or supplies to different locations on the battlefield.
The interaction can be complex. Magic might be seen as a powerful but unpredictable force by the US Army. Some soldiers could be in awe of it, while others might be skeptical. For example, if a wizard were to use the 'Accio' spell to retrieve a weapon from a long distance during a battle, it could change the tide of the fight. However, there would also be issues like how to control the use of magic within military discipline. There could be rules and regulations set up to govern when and how wizards can use their magic in military operations. This would require a lot of cooperation and understanding between the two worlds.
Obviously, his friends Ron and Hermione would be among the first to join. Neville could also be a key member, as he has shown great courage. Then there might be the members of Dumbledore's Army who are still at Hogwarts. The Weasley twins could also be part of it, using their unique magical inventions to give the army an edge in battle.
Neville would likely be one of the first to join. He has always been brave and has a strong sense of justice. Luna Lovegood might also be part of it. Her unique perspective and knowledge of the wizarding world could be very useful. And then there are the Weasley twins. Their skills in magic and their ability to think outside the box would make them great assets.
Harry may decide to have a more intuitive magic system. Instead of relying on wands, which can be lost or broken, the magical beings on his planet could use their minds and emotions to cast spells. The stronger the emotion or intention, the more powerful the spell. And to prevent misuse, there could be a natural balance in the planet's magic. If someone tries to use dark magic, the planet itself could resist and weaken the spell, teaching the user that dark magic is not welcome.