The results of the peace negotiations could be a matter of life or death for people in the war zone.
(not used with the)
a matter of life or death
1. An issue or circumstance that involves or carries the possibility that someone may die. We have to get these donor organs to the hospital right away—it's a matter of life or death!
2. An extremely serious and important issue; a matter or circumstance that may have dire consequences. I hope you're well prepared, because this board meeting is a matter of life or death for the company.