In a fanfiction where Harry Potter leads an army, he would need to be a great leader. He'd have to inspire his troops, which would include people like Hermione and Ron. They could use their knowledge of magic and friendship to hold the army together. The army could also include some unexpected allies, like the giants or the centaurs. This would change the power dynamics in the wizarding world and could lead to a quicker end to the war against Voldemort.
Definitely Hermione and Ron. They are his closest friends and always by his side. Also, Neville would be a great addition. He has shown great courage in the original story. And of course, the members of the Order of the Phoenix like Sirius (if he were still alive in the fanfiction) and Lupin.
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.
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.
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.
It could be about a character named Harry leading a group of retired army personnel in various adventures. Maybe they get involved in solving mysteries or facing threats that require their military skills and experience.
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.
Well, it could be about a new threat emerging in the wizarding world where a droid army is created by a dark wizard who has mastered both magic and Muggle technology. Harry and his friends have to figure out how to defeat this army using their own magic skills and knowledge of the wizarding world.
In fanfiction, if Harry Potter joins the army, he'd likely bring his magical skills. He could use spells for things like reconnaissance, making invisible barriers for protection, or even using the Patronus charm to boost morale. His experience fighting Voldemort would give him an edge in combat situations, and his leadership skills developed during his Hogwarts years would make him a valuable asset in military strategy and inspiring his comrades.