[req] Automatically splitting a post without using the_excerpt or the more tag

I would like WP to automatically split a post without the author having to write a separate post in The Excerpt, and also without having to insert a <!-more-> tag inline with the post.

Surely there is a way to ask WP to display the first x number of characters from a post?

I have searched everywhere and most people seem to answer with ‘use the_excerpt’ or ‘use the more tag’.

Thanks in advance.