death march vs forced march

death march

noun
  • A forced movement of people, on foot, in such circumstances that many die during the journey. 

  • Synonym of dead march (“mournful music for a funeral etc.”) 

  • A project that requires a stretch of unsustainable overwork, or whose participants feel it is destined to fail. 

forced march

noun
  • A movement on foot by soldiers or prisoners of war, who must, in order to satisfy a military requirement, travel at a speed or in adverse conditions that would normally tire them excessively. 

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