Magic could play a role in Spartan warfare. Harry could use spells to create illusions on the battlefield, confusing the enemy. However, the Spartans' strict military code might initially resist such unorthodox tactics. But as they see the effectiveness, they might start to incorporate some magical elements into their battle strategies. Also, Harry's magic could be used in Spartan religious ceremonies, adding a new dimension to their spiritual practices.
Harry's magic would likely be both a source of wonder and suspicion in Spartan culture. His ability to conjure things out of thin air might be seen as a gift from the gods by some, while others would be more cautious. For example, his magic could be used to help in the Spartan's agricultural efforts, like making crops grow faster, but this might also disrupt their traditional ways of farming.
In Spartan society, which values physical strength and discipline, Harry's magic would present a contrast. His magic could be used to heal the Spartans' injuries in a way that is much faster than their traditional medicine. This could lead to a change in how they view physical and magical forms of healing. Also, his ability to communicate with animals using magic could be both useful and strange to the Spartans, as they have their own relationship with nature.