assail vs inroad

assail

verb
  • To attack with harsh words or violent force (also figuratively). 

inroad

noun
  • An advance into enemy territory, an attempted invasion; an encroachment, an incursion. 

  • Often followed by in, into, or on: initial progress made toward accomplishing a goal or solving a problem. 

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