bombardment vs onslaught

bombardment

noun
  • heavy artillery fire 

  • the act of bombing, especially towns or cities 

  • the incidence of an intense stream of high-energy particles directed at a substance 

onslaught

noun
  • A fierce attack. 

  • A large number of people or things resembling an attack. 

How often have the words bombardment and onslaught occurred in a corpus of books? (source: Google Ngram Viewer )