What force played a role in the decline of all four river early civilizations?

Read the excerpt from the history of herodotus, book 2. egypt . . is an acquired country, the gift of the river. this quotation from herodotus, a greek who traveled in egypt, is about how the nile river enabled ancient egyptian civilization to develop and succeed. what specifically was the river’s gift? fertile soil fishing stocks defensive capabilities drinking water

Nazi germany practiced this form of nationalism. cultural religious ethnic political

What is the level of government responsible for things like police and fire, protection, and is led by a mayor or council?