Victory or defeat in war is often as much psychological as it is military. Military forces fight to impose their wills, and at a certain moment, even if the weapons are not yet silent, one side or the other loses heart. Its will to resist breaks, and defeat becomes a matter of time.
http://www.realclearworld.com/blog/2016/04/now_is_the_time_to_break_isis_111793.html
