defend <sectors> {%|sector}
   If the '%' is given, then you will be asked for your password, and, if
correct, the defender for any defended sector in the specified area is
displayed. Otherwise, you need to enter the location of a fort to defend the
given sectors. If no defender is given on the command line, you will be
asked for the defender for each sector in the specified area. When a defended
sector is attacked, assaulted or fired on, the defending fort will attempt
to fire on the attacker. The presence of a defense is indicated by a '%' in
the census listing.