The battle between two terms that feature in history book that have the same name.
Aryans: Unless you are a fan of Hindutva, the Aryans were a group of people(or peoples) who migrated from somewhere in western or central Asia into Northern India sometime in 2nd Millennium BC, from which all of the Indo-European languages of India descent. In the 19th Century, they were considered a separate pale-skinned 'race' (it is now known that these migrants could only have been an elite or at least a small number) that conquered Northern India due to its obvious biological superiority (only to degenerate by mixing with India's indigenous lesser breeds). This theory once gained a lot of fans, especially with a bunch lads in 1930s Germany who once set off on a
Military cum Scientific expedition to Tibet to find the origin of this master race and even received praise by the Dalai Lama for doing so.
Arians: A Late Antique/Early Medieval Christian Heresy which claimed that the Son (Jesus) was derived from the Father (God) and therefore not in an equal relationship with him. This contradicted the Catholic Trinity laid down at Church Councils like Chalcedon that the Father, the Son, and the Holy Spirit were all equal parts of the whole Godhead, making God a being that was both three-in-one and one at the same thing in a theory that nobody really understands or ever understood. If you know anything about Late Antique history this WAS VERY, VERY IMPORTANT and it was condemned repeatedly as a heresy during the centuries in which it was relevant. Arius was a Roman cleric in the era just before the end of the Western Empire, curiously his belief system, which got little support among the established 'Catholic' churches of Antioch, Constantinople and Rome was very influential among the Germanic 'Barbarians' and many such 'tribes' like the Goths converted to Arianism. However, like with the Aryans, it primarily seems to have been an elite thing but, unlike the Aryans, had died out by the end of the 7th century. Despite being infinitely more Germanic than the Aryan Race of India nobody in 1930s Germany ever tried to revive Arianism afaik.