In examining the Darfur Case Study, it definitely appears that this conflict seems "to lurch from impasse to impasse." Why is this the case?

In examining the Darfur Case Study, it definitely appears that this conflict seems “to lurch from impasse to impasse.” Why is this the case?
The response should be at least 350 words.
http://www.crisisgroup.be/interactives/2014/sudan/a-darfur-decade.html