this is "nightline." tonight, breaking news. the u.s. airstrike killing a top iranian military leader. tensions between iran and the united states now reaching a boiling point. what we're now learning tonight. plus, alex trebek. behind the scenes "jeopardy "jeopardy" host. how he's bravely facing his greatest challenge. "nightline" will be right back. greatest challenge. "nightline" will be right back.

good evening. thank you for joining us. we begin with breaking news. in a major escalation in tensions between the u.s. and iran, the top iranian general has been killed in an airstrike while leaving the baghdad airport. the pentagon confirmed the u.s. military carried out the attack. soleimani was one of the most powerful figures in the middle east. he had been the top military man in iran for more than 20 years. this attack comes after iranian-backed groups breached the u.s. embassy two days ago. we turn to kyra phillips who's with president trump in palm beach, florida. >> reporter: when reports broke

tonight, there was one question on everyone's mind. was the united states responsible? well, the president was cryptic. he responded with only a picture, tweeting out the image of the american flag. my white house sources were able to confirm that not only did the strike happen, but it was ordered by president trump. the pentagon announcing that the strike did indeed kill the powerful commander of iran's revolutionary guard corps, qassim soleimani, as well as the head of an iranian militia. and p it was ordered by president trump. now here ithe u.s., republicans are calling this a success, saying president trump made a brave and correct call, but the president is facing questions from his critics on capitol hill, asking if the united states carried out the assassination without authorization from congress, potentially bringing this country to the brink of an all-out war.

>> joining us now is chief global affairs correspondent, martha raddatz. you were on the ground in iraq with soleimani not too long ago. what was his presence like there? >> caller: when isis was taking over towns in iraq, soleimani would often be seen in iraq, traveling back and forth between iran and iraq to help lead the fight, these iranian-backed militias against isis. he was a very strong but very mysterious presence in iraq. he was not high profile by any means, but people certainly knew he was there and certainly knew what he was doing in trying to defeat isis. but i will also say that his presence was felt throughout the war there, because he was responsible for the death of many americans, and i heard soldiers and generals and everyone talk about that, and what the iranians had done and the iranian weapons that were present in iraq and targeting american troops. >> so clearly then this is a

victory tonight for the trump administration, but i would imagine iran will have a response, yes? >> caller: i think it's almost certain iran will have some sort of response, even given what we've heard from them this evening in tweets and that the united states in some way will pay for this.anthing here to look at in any kind of iranian response is whether they take credit for it. remember, with the attacks earlier this year on the saudi oil fields and the drone attacks. they talked about the drone, but they did not talk about the saudi oil fields. they did not take responsibility for those attacks. in fact, the foreign minister of iran told me in person when i was in tehran, that some of those must have been photo shopped, that they weren't responsible for those things. so i think if iran has some sort of response to the killing of soleimani and take credit for

it, they are looking for a larger conflict. if they don't, i think they want to tamp this down. >> martha raddatz, thank you so much. joining us now is abc news military contributor, steve ganyard. what's the latest information you have at this hour? >> we know everything that is out in the public, and that is that soleimani is dead along with the head of this militia group that iran controlled. and so that is the headline that's not going to change overnight. what may change overnight is how the iranians react. obviously, this is something that they'll have to do something about. mr. soleimani is, he is not just a general. he is somebody, almost a demi god. within the eyes of the iranian people. he has been a hero of the iranian people for a long time, their face overseas in their

international adventures, so this is not just some general. this is somebody not only one of the most powerful men in iran but in all of the middle east. >> it seems you would suggest that iran will almost certainly have to respond. >> they're going to have to do something. i think what they do and how much they do is up to them. the administration did two things that were very inre one is they said we will hold iran responsible for anything that happens. that means, no surrogates, no hezbollah, no tankers in the gulf just mysteriously blowing up. no global hawks being shot down. anything that happens, iran will be held responsible by the u.s. they no longer have the ability to hide behind their proxies or surrogates. what they do will be up to them. but they know if they get held responsible that the u.s. very quickly could defeat their conventional military and use them helpless. that's real risk here. it turns into something that becomes a very dangerous conventional fight within the persian gulf. >> based on what you just said,

how likely is it at this point that more u.s. troops will be sent to the region? >> i think the posture that we have there is quite strong. it's certainly enough to deal with anything that the iranian military could throw at the u.s. it just depends on what kind of response comes from it. if the iranians decide to do something quiet, hit back just to show that they did, it will probably be something that the troops there will be able to handle. the real danger here is does it get out of hand. and the iranians respond, try to deflect the anger that is inherent in the iranian people toward the iranian regime. there have been riots ov the past few months. thousands of iranians have been killed by iran security forces. so the iranian regime wants to deflect that anger onto the u.s. that will be part of the calculus in how hard they hit back at the u.s. >> thank you so much. the attack tonight, killing the top general in iran is the latest in the troubled relationship between the u.s. and iran, one that's been ongoing for 40 years, since the

regime took american hostages. but last summer, tensions began to increase once again. the u.s. calling the strike a success. for the iranians, almost surely a call for retaliation. iranian television announcing his death, saying soleimani had been martyred after years of struggle for islam. the department of defense saying it had been done at the direction of the president, adding that this was aimed at deterring future iranian attack plans. it came after continuing tension between the u.s. and iran. 2018, president trump pulled out of the nuclear deal. brokered by president obama. >> this was a horrible, one-sided deal. >> days ago on new year's eve. >> do i want to? no. i want to have peace. i like peace. and iran should want peace more than anybody. so i don't see that happening. >> reporter: in april, the u.s. pame me

ecedend epf ng rrorisnition. >> this will deprive the world's leading sponsor of terror the ability to spread terror around the world. >> reporter: a u.s. aircraft carrier had been deployed to the region. then a series of attacks on international oil tankers in region's shipping channels. >> smoke billowed hundreds of feet high. >> reporter: tit-for-tat leading to an attack on a usa drone. the pentagon claims it was flying in international airspace. but iran claims it was in their territory. the pentagon readies an airstrike, only to see a stunning reverse in course around 7:00 p.m. the u.s. military ready to launch war planes and warships at iranian targets.

trump made a dramatic reversal against the advice, sources say, of former national security adviser john bolton. and secretary of state mike pompeo. but he later told news he changed his mind because the strikes were not proportionate. to the downing of an unmanned u.s. drone. >> i said they shot down an unmanned drone. and here we are sitting with 150 dead people that would have taken place probably within a half hour after i said go ahead. >> reporter: the president denying that planes were in the air and ships in mission before he called off the strike. but that was not the case tonight. tonight the strike went off. we'll have continuing coverage on "good morning, america." up next, alex trebek. what you did not know about the "jeopardy" host's heart breaking cancer diagnosis. to be honest a little dust it never bothered me.

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alex trebek is getting candid with his battle with cancer, tonight revealing his new sense of purpose. >> what is score keeping? >> reporter: with the host in the guinness book of world records, for 36 years, it's been appointment tv. what is "jeopardy ". their day starts early. >> right on time, five minutes to 6:00. >> reporter: first order of the day, answering e-mails and fan letters.

he has been getting more of them since his pancreatic cancer diagnosis. >> throughout my life, i've always wondered how courageous a human being i was. i look at it as it's part of life. does that mean i'm courageous because i'm dealing with it? no. i can be scared to death and i'd still have to deal with it, but i'm not scared to death. so maybe i am courageous. way to go, alex. this week, i was diagnosed with stage four pancreatic cancer. >> reporter: in march, he told the country. >> i join forces with the world pancreatic cancer coalition. >> reporter: in october, he told us what to watch for. >> mid back pain. unexplained weight loss. new onset diabetes. >> reporter: jean and alex trebek have been married 29 years. they have two adult children. what's the toughest part for both of you. >> i think for me it's when i see him in pain and i can't help him. and when he doesn't eat right.

when he has too much diet soda. >> back off, michael. it's always tough for the caretaker. because she has to deal with her worrying about my well-being. >> reporter: after encouraging results from his first round of chemo, his medical condition worsened. he decided he would try whatever comes next. >> i don't mind experimenting. i've got nothing to lose. so let's go for it. >> reporter: the cancer diagnosis shifted his world. >> most of us have open-ended lives. we don't know when we're going to die. because of the cancer diagnosis, it's no longer an open-ended life. it's a close-end life. because of the terrible statistics, survival rates for pancreatic cancer. and because of that and

something else that is operating here, people all over america and abroad have decided they want to let me know now, while i'm alive, about the impact that i've been having on their existence. >> reporter: i'm just happy that people are able to express it right now. >> they have come out, and they have told me, and my gosh, it makes me feel so good. >> he's being so gracious and calling people and writing letters. he's playing the hand he's been dealt, and he is really playing it so beautifully. >> i thought you guys might like my sharing something. >> repleerrom >>viorer.a r:t' is us j intt for speaking about his symptoms. >> thank you, alex. my brother-in-law decided because he was experiencing some of the same symptoms to go and see his doctor. today he found out that he has stage one pancreatic cancer. looks like it's very treatable. so i wanted to say thank you,

because i really feel like you saved his life. >> god bless you, alex. >> so that made me feel pretty good. >> reporter: yeah, you saved somebody's life. >> absolutely. >> reporter: in a taping day filled with nerves, lights and cameras, it just doesn't come up much. stage four pancreatic cancer, a disease that only a lucky few survive. but alex trebek isn't shy about it. neither are contestants. h >> the category was famous phrases. ewrerote, what is we love you alex. >> that's very kind of you. thank you. cost you 1995. you're left with about $5. i read it first, and then i got choked up. because it suddenly registered on me, oh, dear. okay.

yeah. i don't mind getting choked up. my oncologist told me one of the symptoms, if you will, of pancreatic cancer is that you get these moments of depression, of sadness. that's not to say that all of the negative symptoms i'm experiencing are because of the cancer. they're all because of the chemo. i've told people time and time again. cancer won't kill me, the chemo will kill me. and we'll see. >> reporter: next week will be a homecoming for three "jeopardy" legends. >> the greatest of all time. james holzhaur. >> one day record. >> ben jennings. brad rutter. >> reporter: do they make questions harder for these three? >> i hope so. >> all of us are going to come in with a great knowledge base. who's got the guts to go in with a daily double. >> that is going to be

fascinating for the viewers because of the quality of these three players. >> reporter: his greatest of all week. he said he'll stay on the show as long as his skills aren't diminished. but there's one thing the 79-year-old man with all the answers just doesn't know, when his last show will be. you alluded a little bit about retirement. have you thought about what it's going to be like to announce your last winner, to announce your last show and to walk off that stage and you're done? with "jeopardy." >> mm-hm. >> reporter: what do you imagine that will be like? >> it will be a significant e,u, in my mind, rehearsed it already. and what i would do on that day is tell the director, time the show down, leave me 30 seconds at the end. that's all i want. and i will say my good-byes.

i will tell people, don't ask me who's going to replace me, because i have no say in that whatsoever. but i'm sure if you give them the same love and attention and respect that you have shown me for the past 30-however many years, then they will be a success, and the show will continue being a success. and, until we meet again, god bless you, and good bye. >> our thanks to michael. next. the road to success was a little pick me up. up. ♪ oh, oh, oh, ozempic®! ♪ (announcer) once-weekly ozempic® is helping many people with type 2 diabetes like james lower their blood sugar. a majority of adults who took ozempic® reached an a1c under 7 and maintained it. here's your a1c. oh! my a1c is under 7! (announcer) and you may lose weight. adults who took ozempic® lost on average up to 12 pounds. i lost almost 12 pounds! oh! (announcer) ozempic® does not increase the risk of major cardiovascular events like heart attack, stroke, or death.

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trumpand total disaster.mplete leob nurse: these wild attacks on healthcare hurt the patients i care for. i've been a nurse in new york for thirty years. i know the difference leadership can make because i saw what mike bloomberg did as mayor. vo: mayor bloombergow thef uninsured by 40%, covering 700,000 more new yorkers, life expectancy increased. he helped expand health coverage to 200,000 more kids and upgraded pediatric care--- infant mortality rates dropped

to record lows. asd an mor always championed reproductive health for women. so when you hear mike bloomberg on health care... mrb: this is america. we can certainly afford to make sure that everybody that needs to see a doctor can see a doctor, everybody that needs medicines to stay healthy can get those medicines. nurse: you should know, he did it as mayor, he'll get it done as president. mrb: i'm mike bloomberg and i approve this message.

and finally tonight, the greatest lesson of generosity. latonya young is a newly-minted graduate of georgia state university, thanks to guardian angel, kevin esch. he was once her uber passenger, a small act of kindness, paying off nearly $700 of her student debt. >> i was literally blown away, because a stranger has never done that. >> the two sharing a special moment on that special day. it was mark twain w kindness is the language which the deaf can hear and

see. that's "nightline." can you always catch our full episodes on hulu. thanks for the company, america, goodnight.