* To fight Lord Voldemort: The primary reason for forming Dumbledore's Army was to learn how to defend themselves against the Dark Arts and be prepared to fight Voldemort and his Death Eaters. With the Ministry of Magic under control of Voldemort's regime, the Hogwarts curriculum had been altered to suppress any form of defense against the Dark Arts, leaving students vulnerable.
* To resist the Ministry's control: Dumbledore's Army was a way for students to regain their freedom and resist the oppressive regime imposed by the Ministry. The Ministry had been infiltrated by Voldemort's followers, and Hogwarts was no longer a safe haven for students.
* To protect their friends and fellow students: By forming Dumbledore's Army, Harry and his friends aimed to protect themselves and their fellow students from the growing danger of Voldemort's return and the increasing threat of the Death Eaters.
* To restore freedom and justice: The group was also a symbol of resistance against Voldemort's tyranny. It represented a fight for freedom, justice, and the protection of the wizarding world.
* To learn from a trusted mentor: Dumbledore, despite being absent from Hogwarts during the events of the fifth book, left behind his legacy of fighting for what is right. Dumbledore's Army was a testament to this legacy, and provided students with a way to honor his teachings.
It's important to note that Dumbledore's Army was formed in secret due to the oppressive atmosphere under the Ministry's control. The group had to operate undercover to avoid detection and persecution by the Ministry. This secrecy added to the group's sense of solidarity and purpose, as they were all fighting against a common enemy.