Today, I needed to clean up some documentation from an email and I wanted to hard wrap the paragraphs at line length of 50.  After searching a few posts, I found a succinct solution.

14.2. How do I format long lines in a file so that each 
      line contains less than 'n' characters?

You can set the 'textwidth' option to control the number of
characters that can be present in a line. For example, to 
set the maximum width of a line to 70 characters, you can 
use the following command:

    set textwidth=70

Now to break the long lines in a file to the length defined
by the 'textwidth' option, you can use

    :g/./normal gqq