Bound By Purpose.. Multiple attackers and edge weapons defence
It is important to remember that mobility is life, when you are fighting multiple bad guys. If you are in open ground then you must stay in motion. Even if it mean your attacks have less power and accuracy. It wont matter how well you took out bad guy number one if bad guys two and three take you out.
In closed ground mobility is also important. The walls and other structures will be your friends or your enemies. It will simply be a matter of how your view and apply your surroundings.
If you do have to stop and make a stand then its a good idea to use a doorway. This becomes a natural choke point that will bottle neck a group of people into a small area. The frame of the doorway will limit the angle of your adversary attacks and allow you to deal with one bad guy at a time.
Just remember that this is making the best of a bad situation. You must position yourself at the entrance itself and not allow anyone to enter. This also will not work if their is more than one way in.