tonight, david muir on the ground at the ukraine border witnessing firsthand the impact of putin's war. >> many parents telling me it was simply too dangerous to stay. >> families torn apart. women and children forced to leave their fathers, their husbands, behind. as their country comes under attack from russian bombs. video circulating on social media showing the carnage. and the human toll of the kremlin's invasion. plus the former president of ukraine, victor yevshenko, speaks to byron pitts from his secret location. the man who says vladimir putin once ordered him to be poisoned now weighing in on how far he

thinks the russian leader will go. >> do you believe vladimir putin will use nuclear weapons, either in ukraine, europe, or even perhaps the united states? >> this special edition of "nightline," "war in ukraine," will be right back.

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thank you for joining us. the u.n. estimates more than 1 million have fred the fighting in ukraine the past eight days. unicef says 500,000 of them are children. abc's david muir went to the ukraine border with poland where desperate families continue to stream in, leaving the life they knew behind, as the russian military continues their devastating attack. >> reporter: tonight, this is the other sound of war. a boy's anguish, tell is his mother, "i'm tired, i'm so tired." tonight, the humanitarian crisis worsening on the ukraine/poland border. at this train station through the wane we see a crush of need. this is the room set aside for women and children escaping war. so many of the families here have traveled for days. >> it's just an extraordinary thing to witness here.

the train has arrived from ukraine here in pole land. you can see the baby here in this carriage. so many young children brought by their families to safety. as we walk through the crowd here, you can see the sheer number of families who have arrived here. children with their winter coats. but little else. many parents telling me it was simply too dangerous to stay. some had been hiding in basements for days. there is an unmistakable urgency here. people on the phone, families desperate for help. two young mothers, sisters, who escaped ukraine with their children. what has this journey been like? they tell me, this is their fate, what else can we do, we have to keep our children alive. we ask about the fathers. have either stayed behind to fight the russians?

alla says her husband is not in the army, but yes, he stayed behind to fight. you believe you will go back home? like so many of the children we met here, their children carry stuffed animals too. alexi had his favorite dog. >> yes, i do. >> yes, you do, you have your dog. >> reporter: these two mothers and their children spent 22 hours on two trains to get here. >> our children sleep on the floor. >> of the train? >> yes. >> reporter: i asked them about vladimir putin. there is silence and fear. but then they tell me, we want our freedom. >> you want freedom? >> yes. >> you want to keep your freedom? >> yes. >> reporter: tonight the u.n. says there are more than 1 million refugees, 500,000 of them are children. a little girl clutching her doll. in this family from ukraine's second-largest city, kharkiv,

under assault from the russians. >> you came all the way from khark kharkiv? >> yeah. >> reporter: they told me they could hear the bombs, the missiles landing all around them. >> terrifying? and you tried to stay as long as you could? >> my father is still in ukraine. >> reporter: she fears for her father's life. >> i hope -- that he will -- >> survive? >> yes. >> but you don't know? >> we come to home, our ukraine. >> reporter: now a big sister helping to look out for her 8-year-old brother mische. >> his favorite bear? >> yeah, he really loves him. >> reporter: we head into this room where we find strangers who have come from all over, holding

signs. a couple from denmark holding their sign. they have room for eight persons free. we witness their kindness, getting information from a young woman they will now help. >> we all go together. >> reporter: you have offered to take people with you? >> yes. >> reporter: how many people are you trying to take? >> eight people all in all. we went in two cars. >> reporter: what made you decide to do this? >> because we needed to do something. >> reporter: there is so much need here. a little boy sleeping on a bench in the middle of the train station. and families unsure where they'll sleep tomorrow. at daybreak, thousands more fleeing. sirens on the ukraine border. the police escort for the buses filled with families getting out. you can see the buses pulling in one after another. these are all ukrainian families

fleeing their country, coming just across the border here into poland. on board these buses we hear story after story about the mothers and their young children and the fathers who they have left behind to fight against the russians. "don't rush off the bus," she says, "please no panicking, keep an eye on your children." another guard waiting to help. on board, so many of the refugees are children. lifting up this boy, a mother and her sleeping baby and their one bag of belongings. she gets help with her baby. the guard holding him. and then back to mom. she whispers, "don't worry, mommy's here." she kisses her baby. and we find the boy with the superhero backpack. are you a superman? yeah, you're a superman? >> reporter: he's 5. >> you're 5? you're 5?

>> reporter: he tells me they took a train and then a bus. he also tells me his father is fighting in the war. >> your father is still at the war? your son told me that his papa is fighting against the russians. what did you say to him before he left? >> reporter: she tells me, he told them to go because it was terrible, they could hear the missiles the russians were firing all around them. how do you explain this to your children, what do you say to them? she says, "my 8-year-old daughter is old enough to understand the danger."

wiping her tears, she holds her. a kiss to her forehead. as you can see, there's a crush of families here who have just arrived from ukraine. this is the shelter that they have set up here, at least in the short-term, to try to get these families some answers. this young woman, a volunteer, telling them they will now choose a country where they will go next. germany, austria, italy. we see the line of people listening to her, realizing they must choose now where they're going to live. she was telling you all of these places you can go. have you thought about that? where you want to go? she tells me they're planning to go to vienna. can you believe that you're being forced to choose another country to go to?

"i want to be away from the danger," she says, "so i can have my children live in peace." a son hugs his mother after what he's heard. the tears of a mother, yeah. their father staying back too, to fight the russians. do you worry about your husband? "yes, but he told us to go." you're thinking about your father? "very much," he tells me, "i'm having a hard time, i love him." watching it all, his younger sister zlata. please be safe. please be safe. with so much need here, that young volunteer who came from germany helping these families, revealing to me one of the things they need most right now. >> the problem is that we can't find drivers to drive to the

countries. that's the only problem we have. so we really need drivers. >> to get them there? >> yeah. >> reporter: they need more help for the families who have made it out. but also help for people still trying. there are workers and students living in ukraine from africa, asia, and other regions of the world who say they've been stopped at train stations and border crossings. pira, an immigrant from congo, said as he waited to board a train, he was told only women and children. but then watched as some ukrainian men were allowed to board, describing it to our marcus moore. >> we're taking some men. i say, how is it possible? you just said only women and children. so now you are taking ukrainian white people, why? are we not people? like them? >> reporter: tonight, ukraine's foreign minister has now acknowledged the problem, saying they're taking steps to ensure

foreign nationals are allowed to leave the country. and pira is now here in poland. so many of the refugees fleeing ukraine, crossing the border on foot. the long exodus for so many of these ukrainian families who say their journey has been days long. mothers carrying their children. the boy carrying his dinosaur. they come by foot, by bus, and by train. and at the train station, the little girl wearing hearts and holding her unicorn. her mother holding her. >> our thanks to david. up next, our exclusive interview with the former president of ukraine, a man who has seen what putin can do. tackling tough messes can take more time than you have, but mr. clean clean freak delivers the power of a deep clean in minutes unlike bleach sprays, clean freak starts deep cleaning on contact with three times

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♪ former president of ukraine victor yushchenko still bears the stars of an assassination attempt he says was orchestrated by vladimir putin. 2004, yushchenko became severely ill. it was later determined he had been poisoned. he remains in ukraine and has been hiding. earlier today, i had the pleasure of speaking with him. give us a sense of what's happening on the ground, where you are, what you're hearing from family and friends around ukraine tonight. >> translator: there is this feeling that we're witnessing a big tragedy and for people of my generation it's a huge tragedy.

we could never, ever in our lives imagine that something like that could happen to ukraine. >> have u.s. sanctions been effective in this moment? and what more do you think joe biden and america should be doing to stop this war? >> translator: i think that america is reclaiming its leadership in the world. the steps that joe biden is taking speak to the high ambition and politics of taking responsibility. that's why the ukrainian nation is very appreciative. we are very grateful to america for your leadership and example that many countries followed, including those in europe. i think for our conversation, it's important today to find the weak points of russia. because i'm confident russia is not just waging war on ukraine, but against the whole world. and ukraine is actually fighting

against russia on behalf of the whole world. >> president zelenskyy, people questioned whether he was qualified to lead ukraine. now he's viewed a hero around the world. what would you advise him now, what are your concerns for him now? >> translator: i think that president zelenskyy is doing very important work, and the main result that we have now, that is also our biggest strength, is the consolidation of the ukrainian nation. it's possible that we've not been this united in 30 years. tragedy and pain can unite. >> you are, ukraine is outgunned and outnumbered. ukrainians shedding blood to protect your country. how can you possibly defeat

russia? >> translator: the most important thing here is to say that in the last 20 years, despite all the internal bickering, there was a democratic development in ukraine. democracy and development helped create the united ukrainian nation. russia didn't expect it to be so strong and united. russia's never in its history encountered such determination. such democratic spirit. a spirit for freedom. so they were completely unprepared for that. and russia will never be able to defeat ukraine. ever since the mongols tried to invade ukraine, this is probably the biggest onslaught on our territory. but in terms of spirit, in terms of understanding, this totalitarian russia cannot defeat ukraine. >> do you believe vladimir putin will use nuclear weapons, either in ukraine, europe, or even the united states? based on what's going on right now in ukraine? >> translator: in his rhetoric

right now, he uses the words nuclear threat abundantly. his occupation of chernobyl and the nuclear plants is his idea of being a macho man, that he is so strong he can exploit nuclear threats to achieve his goals. i do not think that we'll find any people in the russian military, even as disorganized as it is, or any two officers, who will be ready to turn the key to launch nuclear rockets towards ukraine or anywhere else. i believe that for the whole world today, in the bigger picture, that rational russians understand well today, that is putin is in an absolute extreme isolation. that is why every day, his reputation as the russian president declines and his political beliefs, including nuclear inclinations, are devaluing fast. >> at this point, what can the world do for ukraine? >> translator: if you ask what a

ukrainian soldier wants to have on the warfield, every soldier's first sentence would be, closed air space over ukraine. i think it is an understanding that the achilles heel of the ukrainian defense is strategic bombardments by russia and other types of attacks through the sky. close the air space in ukraine. it's in your power. you can do it. >> victor yuschenko, thank you so much for your time. we wish you and your country the very best. >> thank you very much. my heartfelt thanks to you and good luck to you. when we come back, a "final thought." and all night. prilosec otc prevents excess acid production that can cause heartburn. so don't fight heartburn, block it with prilosec otc. there's a different way to treat hiv. it's every-other-month, injectable cabenuva.

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♪ finally tonight, the horrors and heroism we've all watched and heard from ukraine these past many nights remind us of the prophetic words of an american army veteran who fought the nazis in world war ii. years after his service to our country in war, medgar evers became the secretary of the naacp and a civil rights leader.

in the year he was assassinated in mississippi in 1963, evers said, quote, freedom has never been free. true then, true now. that's "nightline" for this evening. thanks for the company, america. have a good weekend. be safe.