there are signs of life in the city, but as special correspondent jane ferguson reports from raqqa, itny ways, a city of the dead, after isis defeat. >> reporter: no place embodies the devastation of the war against isis more than raqqa, the islamic state's formerta ca the city that isis prized so dearly, devastat bombing campaign to take it from them. a year and a half after thosebo s stopped, the city is in ruin little more than a grey expanse of smashed concrete. down below, yasser khamis drives an ambulance through the city, but there is no one here left to save. hs teams now collect the dead, and he takes us to a recently discovered mass grave. >> ( translated ): we were surprised by the number of bodies there. people came to us and told us about this grave. this land is agricultural land. it belongs to people, and the owners want it back. so we are removing the bodies.s >> reporter: tiet, tree- lined field became a grave for more than 400, khamis us. it's a last resting place for both isis fighteim and their vi here they lay together, side by side ideath. >> ( translated o the peo

for the pbnewshour, i'm jane ferguson, in raqqa, syria. >> woodruff: today, the north atlantic treatyanization turns 70 years o, and nato's foreign ministers met here in washington. they endorsed a package of support for ukraine, whichtes still the f europe's only active war. here's nick schifrin. >> schifrin: 70 years ago today rld's longest-running military alliance was signed into existence, and president truman vowed nato uld not be a threat to the soviet union. >> there are those who claim that this treaty is an aggressive act on part of the nations that ring the north lantic. that is absolutely untrue. >> schifrin: but today, as it did 70 years ago, nato is takinp opposed by what is now, russia. and nowhere is that more obvious than ukraine, now five years into a war between the ukrainian litary and russia-backed separatists. late last year, russian ships rammed ukrainian ships in waters both navies are legally allowed to use. anrtoday, nato announced ma steps to support ukraine, ofincluding more presence nato ships,ore surveillance of the russian navy, and more training of ukra

our own jane ferguson habeen on the ground reporting.she's been capturing some of these heartbreaking images of children caught in the middle and starving. what is keeping your teams onfr the groun being able to get the food and aid to these children? >> yemen is the eath's greatest catastrophe. literally, a nation of 30o million ple, 20 million people food insecure, 12 million people on the bri of starvation. and we are doing everything we can to get access we need the funding is now coming in to the degree we need. but access is a critical dynamic and issue that we face every single da. there are people in harm's way, trying to get food out into the hinder lands where the people that need it. we say to all sides in this war, "don't let these innocent beople ictim to this conflicts." the only way you're going to solve the proem in yemen s end that war. it needs to be ended. >> nawaz: that access, i should mention, is because of the insecurity. the violence has been thescalating. saudi-led coalition air strikes continue. there were just