Moving forum to subdirectory without breaking links

[Vcize]

I currently have my forum in my root directory. I'd like to put a blog on the root directory, and move the forums to a subdirectory (/forum).

The move seems easy enough, but what about the external links to internal pages I already have?

For instance <mydomain>/showthread.php?t=172 would need to be <mydomain>/forum/showthread.php?t=172

My first thought would be an .htaccess redirect, but then that would mess up the blog I put on the front page (it would replace <mydomain>new-blog-post with <mydomain>/forum/new-blog-post, which of course wouldn't exist.

Is there a way that vbulletin handles this? I know I'll have to change my site URL to <mydomain>/forum, will that auto redirect any vbulletin pages in the root to the new /forum domain?