Can any Ummah (nation), however powerful, destroy another if Allah does not will it?
No Ummah, however powerful, can destroy another, except if Allah wills it. Indeed, nothing occurs in the universe without His Permission and Will. (Part No. 3; Page No. 183) Allah says in the Qur'an:
But you cannot will, unless Allâh wills. Verily, Allâh is Ever All-Knowing, All-Wise.
Allah (Exalted be He) also says:
And you cannot will unless (it be) that Allâh wills - the Lord of the ‘Alamîn (mankind, jinn and all that exists).