Google not indexing amended URLs

I recently had to amend some blog articles as their URLs were very long and convoluted.

I didn’t put redirects in place as they weren’t performing particularly well in search and thought that google would drop the old url from search after it starts to 404 and index the new url (which I now know is a mistake and was probably me being a little lazy on my part).

Now i’m getting an issue where the new URLs won’t index and google search console says the reason is because it is duplicated content, due the old url being canonical. I'd like to get these back into search as I'm hoping to improve these pages.

I’m hoping to fix this mistake getting all the old URLs and setting up redirects that point to the new urls, should this work?