air raid vs exchange of fire

air raid

noun
  • A passing-heavy offensive scheme based on a shotgun formation with four wide receivers and a single running back. 

  • An attack on a surface target by aircraft. 

exchange of fire

noun
  • The act of shooting at each other by antagonists armed with guns. 

How often have the words air raid and exchange of fire occurred in a corpus of books? (source: Google Ngram Viewer )