tonight, terror in kabul. two suicide bombers killing at least 13 american service members and dozens of afghans just days before the u.s. deadline to withdraw, wreaking havoc on the race to evacuate tens of thousands. >> they are in danger, the whole family is in danger. >> slamming an already desperate situation. >> these are devastating, heartbreaking scenes here. >> the worst fears of american commanders realized. president biden vowing retribution. >> we will hunt you down and make you pay. >> as america's longest war draws down, we're with the families who have sacrificed the most. >> i've gotten a knock on my door, i had a family member killed in action.

it's so difficult. >> this special edition of "nightline," "terror at the gate," will be right back. hind . unlike ordinary memory supplements, neuriva plus fuels six key indicators of brain performance. more brain performance? yes, please! neuriva. think bigger. (vo) imagine a visibly healthier pet in 28 days. purina one. natural ingredients... in powerful combinations. for radiant coats, sparkling eyes. purina one. one visibly healthy pet. try these purina one true instinct formulas for dogs.

♪ thanks for joining us. for the first time in more than a year, the staggering u.s. death toll in afghanistan has grown. at least 13 service personnel killed along with dozens of

afghans. the closing salvo in america's longest war. abc's senior correspondent ian pannell, who just left the country, leads us off from doha. >> reporter: we'd already seen a decline of the numbers of people being evacuated the last couple of days. as the retrograde takes place and following this incident, and there will be increased restrictions on the numbers of people being able to be brought safely into the airport, then surely that decline is going to continue. isis-k as they've shown now is perfectly capable of conducting attacks. and because when the taliban swept through many cities they also opened all the prisons, that didn't just include taliban fighters, it also included isis. and general mckenzie also said that one particular concern was the possibility that some fighters couldet touho serity get o flht w on las pack with hundreds o afghan

refugees, and detonate a device. the risk had already existed for u.s. troops, other nato troops, and in particular, for refugees, they've just got worse. juju? >> our thanks to ian. the attack at the airport may have complicated evacuation efforts but it didn't stop them. the white house says approximately 7,500 people were flown out on thursday. but the bombings and the loss of so many lives is the realization of the greatest fears of american commanders. from crisis to catastrophe. after two suicide bombs exploded near kabul's international airport, the worst mass casualties suffered by american forces in a decade. >> these american service members who gave their lives, not to overuse the word but it's totally appropriate, they were heroes. heroes who have been engaged in a dangerous, selfless mission to save the lives of others. >> reporter: the first suicide

attack happened here at abbey gate, followed shortly by a second blast at the nearby baron hotel just 200 yards away. shell shocked and bloodied, dozens of victims rushed to the hospital by whatever means necessary. it's become a darkly familiar routine for afghans, who have endured years of this. the blasts coming after days of warnings about potential terrorist attacks. last night the state department issued a bulletin about an imminent terror threat, urging all u.s. citizens to evacuate the area, including abbey gate, immediately. the ambassador with this warning just hours before the blasts. >> being part of these huge crowds that are meeting around the gates and entrances to the airport is dangerous. we're obviously concerned about our own people as well. >> it was obvious to me that we had very good tactical intelligence on the threat picture in and around the airport. the warnings that came out were specific, and unfortunately played out almost exactly as

they had determined. >> reporter: the group claiming responsibility, isis-k, a fundamentalist offshot of islamic state and enemy of the taliban. >> the threat from isis is extremely real. we've been talking about this for several days. we saw it actually manifest itself here. >> for those who carried out this attack, as well as anyone who wishes america harm, know this. we will not forgive. we will not forget. we will hunt you down and make you pay. >> reporter: in the midst of a massive evacuation operation, more than 100,000 people have left since the beginning of the month. but thousands more are desperately waiting. this was the scene at the abbey gate yesterday where one of the blasts occurred. abc's ian pannell was there on the perimeter wall, guarded by marines. >> abbey gate! >> reporter: those in the guard tower keeping watch on the

crowds below, including one man waving his blue u.s. passport. >> i can help you get in, you'll have to wait over there! >> these are devastating, heartbreaking scenes here. these people down here have stood in sewage water up to this knees, and this is what i've been saying, this is the difference potentially between the life-saving work that's been carried out by the military here and potentially death by the taliban. less than five yards. >> reporter: the taliban today condemning the attack. tonight with as many as 1,000 americans still in afghanistan, it's a race against time as the august 31st deadline for american forces to withdraw just days away. >> i think you'll see jihadists through afghanistan right now who want to be there for the 20th anniversary of the attack, september 11th. it is not you could say, obviously, in the united states' interests in the region and

overall pattern of terrorist efforts. >> reporter: despite warnings the president stubbornly sticking to that deadline. >> i've instructed the military, whatever they need, additional force, i will grant it. but the military, from the chairman of the joint chiefs, the joint chiefs, the commanders in the field, have all contacted me one way or another, usually by letter, saying they subscribe to the mission as designed. to get as many people out as we can within the time frame that is allotted. >> reporter: for those still struggling to get out, every day is filled with dread and uncertainty. hawad is an american citizen. his wife and two small children are as well, living in southern california. last month his wife and kids went back to afghanistan to visit a sick family member. now they're trapped. >> we have been trying

everything possible to get them out, but there's no way. we have tried everything to do so, but we cannot, unfortunately. >> reporter: my colleague, alex per shea, spoke to hawad earlier today. >> they are in danger, the whole family is in danger. i'm afraid for their life, you know? i may lose them, they may die. >> reporter: communication with them in afghanistan has been a challenge, but hawad and our team were able to speak to her today. >> very scary. we were deciding to go to the airport today. and we're thankful that we didn't go. >> what is your plan now? >> not knowing if the airport gates will be open tomorrow, we were hoping to get out of the country by august 31st. but now they can't say when it will be open. >> reporter: for kelly mchugh stewart, today's bombing and the lives lost is a horrible

reminder of the legacy of the war. >> got the knock on my door. had a family member killed in action. it's so difficult. >> reporter: her father, u.s. army colonel john mchugh, killed by a suicide bomber in kabul in 2010. >> today is not the day for anger because it truly is just so devastating and sad. but over the past two weeks, there has been a lot of anger. since my dad's death, you go through the normal grieving process. then i started to get curious and wondered, what is this war for, what is our end game, what are we doing in afghanistan? no matter where i've looked, i could never find answers to those questions. >> reporter: those questions echo the reason behind the president's decision to get out, that no more u.s. lives would be lost in this, the never-ending war. now the overwhelming worry that this bombing won't be the last attack. >> right now our focus is actually going forward, assuring

that another attack of this nature does not occur. as you know, typically the pattern is multiple attacks. >> reporter: which is why 6,000 american troops still in afghanistan, executing one of the largest humanitarian airlifts in history. >> we will not be deterred by terrorists. we will not let them stop our mission. we will continue the evacuation. >> reporter: the bravery of those troops in harm's way always on their minds. especially their fallen comrades who today were hailed as heroes. joining me now, nbc's chief global affairs correspondent, martha raddatz. we're learning a lot more about isis-k, the isis affiliate enemy of the taliban, today claiming responsibility for the attacks. and president biden vowing retaliation. what can you tell us about the strike plans he's asked his commanders to prepare? >> i am sure they are just putting those together now, juju. they always talk about

contingency plans. but president biden did say he thought commanders knew where isis leadership, isis-k leadership as it's called, was in afghanistan and was very firm about hunting them down. and we will go after you at the time and place of our choosing. they won't really choose the place because wherever that isis leadership is is where they would attack. you know, they had very good intelligence about a possible attack. they were alerting americans to get away from that gate. but it happened anyanyway. so intelligence is never perfect. and it will probably take awhile before they find those isis commanders and can plan some sort of strike. but i believe this is something the u.s. will carry out. >> and expand on that a bit, martha. it's been a gut-wrenching day for the military. you've been on the ground in recent weeks with our soldiers. how will this terror strike, do

you think, impact the final days of the mission and the morale going forward? >> you know, i've talked to so many members of the military this past week who are so upset about what they were seeing anyway, so worried about their afghan partners. and now not only to lose afghans but all of these marines and navy corps men and army -- it is a devastating, a devastating thing to be around. and i think all the more devastating, juju, because, frankly, it has been a long time since the military has suffered a mass casualty like this. at least a decade in afghanistan. we were getting out of these conflicts, and all these beautiful pictures of our service members helping people, going out there, taking babies, pouring water on little kids. this was a missio that made them feel better, that they were trying to get all of these people out of there, evacuated, and into safety. ad certainly the people who had helped them in conflicts before.

so this is a heavy, heavy loss. but they'll put their heads down, and they'll try to finish this mission to the best of their ability. >> so eloquently said, martha. just days away from that august 31st pullout date. thank you so much, martha raddatz. >> thank you, juju. up next, what went wrong? and what's next for u.s. forces in the region? people everywhere living with type 2 diabetes are waking up to what's possible with rybelsus®.

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♪ now to gain even more perspective on today's deadly terror atabs, earlier i spoke with two veterans of iraq and

afghanistan. author and former marine elliot ackerman who served tours of duty, republican congressman adam kinzinger who is still an air force reservist. thank you both for joining us. representative kinzinger, let me start with you. 13 u.s. troops were killed today, the most in a single day in a decade. was this avoidable? >> look, in congress we got a brief on this a couple of days ago with the most crystal-clear evidence i've ever heard in terms of what's coming through intel. and so the real question is, how did this, these bombers, slip through the taliban lines? i think that's the question. we're relying on the taliban to secure that perimeter. we'll find out if it was avoidable. but it's certainly tragic. >> mr. ackerman, isis-k is claiming responsibility for this bombing. tell us about the power vacuum created when the government fell so quickly.

>> i think it's something we've seen occur time and again. we saw it occur in iraq after the withdrawal in 2011 which led to the rise of the islamic state three years later in 2014. we're seeing it occur right now in realtime in afghanistan when isis-k has now announced itself. if there's any sense that the taliban can keep al qaeda from arriving in afghanistan, that should be totally dispelled by today's events. they're there, and they've announced themselves. >> president biden said today these terrorists will not win that he's going to hunt them down and make you pay. and yet many of the critics of this withdrawal described it as a failure of intelligence. how reliable is our counterterrorism effort at this point? >> i don't think it's very reliable. it doesn't mean we're not going to try to find targets. we may find some isis-k targets to kill, maybe even the leaders of this attack if we're lucky. but keep in mind, every kind of counterterrorist operation has to have people on the ground. we look at our success against

isis and iraq and syria. we had people on the ground embedded with local forces. it's hard to imagine that, without having people on the ground, we're going to be able to successfully attack and put a serious dent if not dismantle isis-k. we'll get some payback, that's fine, but i think the visual of america leaving, and america leaving after taking casualties, 13 dead at this point, it's certainly going to be a boon to jihadist recruitment. that's what i worry about as well. >> mr. ackerman, you've been working with a network of former military people for nearly two weeks to try to get people out of afghanistan. tell me about some of those desperate messages that you've been absolutely inundated with, and what does that say about the u.s. military's plan or lack thereof to evacuate? >> i don't think you can pin any of this on the u.s. military. the u.s. military have behaved nothing short of heroically the last two weeks. the final group that i was able

to help coordinate into the airport of afghan refugees and also some american citizens was 29, and we got them through abbey gate 20 minutes before that blast occurred today. what we're seeing is a massive policy failure, a massive failure to execute on the part of president biden and his administration. there were members of congress in very strong voices warning about just such a series of events as we're seeing occurring as far back as april, and the administration refused to heed those warnings. >> you've worked in policy in d.c. at the white house. what policy failure do you point to, and what could have been done better? >> many people in the media compared this to saigon. it's worse than saigon. you need to only look at a map to see in vietnam, when we were back in that country, evacuating, you had hundreds of miles of coastline. afghanistan is landlocked so it doesn't take an expert in grand strategy to realize that if

you're trying to get everyone out of a single airport, it's going to be a total disaster. we should have had places like bagram air field, kandahar air field open. a single access point, it's a corner we backed ourselves into, we backed our military into. >> you flew tours over afghanistan and iraq. do you think that responsibility lays at the foot of president biden and his policy planners? >> i think, frankly, both parties failed the american people in this. i think president trump negotiated an awful deal. he was talking about how unimportant afghanistan was while he was negotiating that deal. and they didn't enforce the deal during that time. well, then president biden comes in. he's reversed a number of president trump's stuff, including sanctions on the russian pipeline. he owns the tactics of this. so he made the decision to withdraw. we vacated bagram. we basically were in a position where we saw that everything was collapsing, and instead of at

least defending kabul for the moment while we got everybody out, we end up having to rely on taliban to protect -- i mean, our sworn enemy, to protect the air field. both presidents bear blame for this. but certainly at this moment, this is on joe biden and nobody else. >> gentlemen, thank you both for your insights, both for your service, and for joining us today. up next, a final thought. ...the itching ...the burning. the stinging. my skin was no longer mine. my psoriatic arthritis, made my joints stiff, swollen... painful. emerge tremfyant™. with tremfya®, adults with moderate to severe plaque psoriasis... ...can uncover clearer skin and improve symptoms at 16 weeks. tremfya® is the only medication of its kind also approved for adults with active psoriatic arthritis. serious allergic reactions may occur. tremfya® may increase your risk of infections and lower your ability to fight them. tell your doctor if you have an infection or symptoms

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♪ stay with abc news for continuing coverage on the ongoing situation in afghanistan. that's "nightline" for tonight. you can watch full episodes on hulu. see you back here