redirects from 1 subdirectory to another

Hi I have a bit of a weird situation. I have a website, let's call it domain.com. However the actaul site is domian.com/blog and domain.com just forwards to domian.com/blog. Now we are building a new site at domain.com/dev. The problem is that we want all the old URLs to forward ot the new ones with 301s. I cant figure out how to do this. I added a 301 redirect plugin to the install at domain.com/blog and added: (wildcare) that / should forward to /dev but then when I went to the hompage of domain.com/blog to test, it went to domain.com/blog/dev since it thinks the /blog is part of the domain. Do I have to remove the forward of domain.com > domain.com/blog and add the redirects there? Or some other way?