institute of peace and astrid ziebarth of the german marshall fund in berlin.nk you both so much. >> thank you, gwen. >> woodruff: while much of the world's attention turned away from ukraine this summer, the fighting there largely raged on, killing and wounding more fighters and civilians and continuing displacement in the country's east. yet another cease fire between russian pro separatists and ukrainian forces went into effect this week, but many aren't holding their breath. chief foreign affairs correspondent margaret warner has this update. >> warner: for children across ukraine, even in war-torn donetsk, this is back-to-school week, with its traditional assemblies and ceremonies. it provided the occasion for a cease-fire that went into effect yesterday. but was violated today near rebel-held luhansk, when a ukrainian army vehicle was ambushed, killing two people. indeed, now in its second year of conflict, cease-fires brokered by european powers have repeatedly failed to stick. instead, trench warfare rages on, in eastern ukraine, between government troo