Interesting that they didn't choose the Navy, more traditional for the royal family and more patriotic for the island nation.
Harry already had a bit of a rebelious streak. Maybe it was his way of "being himself" and more power to him. I wish him luck and much success.
Actually, historically the Army isn't that uncommon a choice for royals, in recent times, the Navy has certainly been dominant, but over the years other services have featured quite often. Edward VIII (as Prince of Wales) was an Army officer in the First World War and even won the Military Cross, despite not being allowed to officially serve in a combat role.