Honestly, there is very little defense in AH. Sometimes a mission comes in, and enough people up to deal with the attack, and the attackers just move to another undefended base. Othertimes, defense is seen as a group of people hovering over their field, seeming just waiting for their hangars to go down. Once and awhile you get a good fight going. When I think of offense being the best defense, I don't think about leaving from another field and milking someplace else. I think about leaving from the field that is being attacked, beating them back, and then taking the field they were flying from. I get the feeling though, very often in AH, this is not what people mean when they say "best defense is a good offense."