Summarize this article in one sentence.
If your territories are not well fortified, then they will be vulnerable to attack from your opponents. To keep your territories safe from attack during your opponents' attack phases, move your pieces where you want them before ending your turn. Move your pieces to different territories at the end of your turn. It is in your best interest to move pieces to your border territories that are more vulnerable to attacks by your opponents. There are two rules on how you can move your pieces:   Standard Rule: Move any number of army pieces from a single territory into an adjacent territory occupied by you.  Alternate Rule: You can move pieces anywhere, as long as the starting point and destination can be reached by going through a string of adjacent territories under your control. In order to retain control of the territories that you are moving army pieces from, make sure that you leave at least one of your army pieces on each territory that you own. Otherwise, you will no longer have control of the territory.

Summary:
Understand that you cannot move armies around until your next attacking turn. Fortify your territories. Remember to leave at least one army piece behind.