pioneering vs rearguard

pioneering

noun
  • A scoutcraft skill that involves building structures using staves and knots. 

  • The activity of the verb pioneer. 

adj
  • Involving accomplishments or activities that have not been done before, or developing or using new methods or techniques. 

rearguard

noun
  • The rearmost part of a force, especially a detachment of troops that protect the rear of a retreating force. 

  • The defence, collectively the defenders. 

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