If Harry Potter leads an army in fanfiction, there would be many possible members. The students from Gryffindor, Hufflepuff, Ravenclaw and Slytherin who oppose Voldemort could join. The Weasley family as a whole would be likely to be part of it. Some of the magical creatures such as the house - elves might also volunteer, especially if they see a chance to gain freedom through helping Harry's cause.
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.
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.
It could be a Death Eater in disguise. They might be trying to get rid of Harry once and for all to please Voldemort. They could have slipped the poison into his food or drink when he least expected it.
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.
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.
Hermione would be a great partner. She is extremely intelligent, well - read in magic, and has a great sense of organization. She could handle all the research, paperwork, and strategic planning in the company.
Maybe it's Dumbledore. In some fanfictions, Dumbledore is portrayed as a very father - like figure to Harry. Feeding Harry from a bottle could be a way of showing his deep care and protection for Harry in a different, more nurturing way than we usually see in the original series.
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.
There's a chance he meets a group of nomadic magic - users. These are people who travel across the universe in search of new sources of magic. They could introduce Harry to different forms of magic that are not based on the traditional elements like fire, water, earth, and air that he's used to on Earth. Instead, they might use things like starlight or cosmic energy as a basis for their spells.
There's also a chance that Neville Longbottom could be involved in a cheating situation. He might have grown into a very different person in the fanfiction, and due to some complex emotional and social factors at Hogwarts, he cheats on his significant other. This would be quite a shock as Neville is usually seen as a very loyal character.
His friends from the Hidden Leaf Village might help. For example, Sasuke could be a powerful ally. He has his Sharingan and his own set of powerful jutsu.