draw a line in the sand vs thwart

draw a line in the sand

verb
  • To lay down a challenge; to provide a test of commitment (often one which carries a high risk) to a cause. 

  • To create a real or artificial boundary or distinction between (two places, people or things). 

  • To indicate the threshold or level above which something will become unacceptable or will provoke a response; to create a boundary and imply or declare that its crossing will provoke a (negative) response. 

thwart

verb
  • To cause to fail; to frustrate, to prevent. 

adj
  • Placed or situated across something else; cross, oblique, transverse. 

noun
  • A seat across a boat on which a rower may sit. 

  • An act of thwarting; something which thwarts; a hindrance, an obstacle. 

  • A brace, perpendicular to the keel, that helps maintain the beam (“breadth”) of a marine vessel against external water pressure and that may serve to support the rail. 

How often have the words draw a line in the sand and thwart occurred in a corpus of books? (source: Google Ngram Viewer )