tonight on "nightline," breaking news. a secret missile strike. the u.s. goes after yet another top terrorist leader, the man considered the primary threat to america, after osama bin laden. and, we have exclusive new details on the operation that brought bin laden down. plus, nature's cutest. it's something only very few humans have ever witnessed before. tiny balls of fluff taking their first peek at a big, white world. our cameras are invited on a rare expedition. it's a polar cuddle fest. and, the mom report. what do most moms say they want for mother's day? what country is rated best in

the world for mothers? and where does the u.s. rank? we'll tell you. >> announcer: from the global resources of abc news, with terry moran, cynthia mcfadden and bill weir in new york city, this is "nightline," may 6th, 2011. >> good evening. we begin with breaking news at the end of this extraordinary week in the war against terror. american officials confirmed tonight that a drone missile attack came very close to killing a terrorist thought to be the most powerful operative after osama bin laden. we'll have more about that later in the broadcast. but first, martha raddatz has an exclusive look inside the months of spying that led up to those navy s.e.a.l.s storming osama bin laden's compound. >> reporter: take elements from every spy movie, thriller and action adventure you have ever seen and you have the reality of this operation.

the raid itself was beyond daring. but what proceeded it was months of pain staking, secretive and dangerous cia work. in addition to the survey lens and satellites above, we have now learned there was a secret safe house, right in abbottabad, with cia spies inside. the house was likely far from the bin laden compound, so as not to raise suspicions. elevation was important, as well, given those high walls around the compound, and the third floor, where bin laden was living. cia director leon panetta will not confirm there were spies on the ground, but clearly, this information did not come from overhead satellites. >> we could see close and we could see some of the members of the family on that third floor. >> reporter: one way reflective glass helped hide the spies and their equipment.

portable cameras were likely used as well. >> we have a variety of equ equipment you can hide. something you might leave outside disguised as a rock or, you know, just a piece of litter, trash. >> reporter: we now know that the cia spies were tracking a taller man in the courtyard who took regular walks. they referred to him as "the pacer" but could never get a clear enough shot to determine if it was, indeed, bin laden. bin laden himself was smart enough to stay off cell phones, away from the windows and did not talk in the courtyard. so, there was never any positive i.d. before the raid. but the number of family living up there matched the number in bin laden's. the pacer was taller. trash was burned. high walls, that was enough circumstantial evidence from the survey lens to make the mission a go. intelligence analysts are only now scratching the surface of the mountains of evidence seized

by navy s.e.a.l.s inside bin laden's compound. but key details have begun to emerge about just how operati operationally involved in al qaeda bin laden continued to be. and how intent the terror network was on developing new strategies to attack america. among the targets, big cities, like new york, los angeles, chicago and washington. >> what i see here, at least for now, is that bin laden, the engineer, who wants to look at the structure of possible attack targets, was asking questions and was getting information. >> reporter: officials say a hand-written notebook was found at the compound with discussions of a plan to derail american passenger trains, prompting this homeland security bull lynn. "as of february 2010, al qaeda was looking into trying to tip a train by tampering with the rails so that the train was fall off the track at either a valley or a bridge."

additional materials found contain information about other inf infrastructure targets, such as dams and the water supply, as well as information about al qaeda safehouses and al qaeda leaders. and for the first time today, a look behind the scenes on that tense sunday for president obama, as the white house released video of the president congratulating his team after bin laden was killed. >> you guys did a great job. >> they did. >> reporter: with each new detail of the complexity of the over ten-year long american hunt for bin laden emerge, a clearer picture has begun to take shape about just how much one man has cost this country. not just in lives, but in money. taking into consideration everything from the economic toll of the september 11th attacks, to the heightened security put in place over the last ten years, to the new programs developed to prevent further attacks, to the two wars

being waged in afghanistan and iraq to the actual direct physical hunt for bin laden, some are placing the cost anywhere between $250 billion to a staggering $3 trillion. and while many, including the president, have indicated that this does not mean an end to the so-called war on terror, with one of the key players dead, things are bound to change. today, secretary of defense robert gates spoke about the death of bin laden while touring a military base in north carolina. >> in terms of the situation in afghanistan, i think that there is a possibility that it could be a game-changer. >> reporter: how the game changes, of course, remains to be seen. >> martha raddatz joins me now from washington. martha, breaking news in just the last couple of hours. what's going on? >> reporter: well, there was a drone missile strike in yemen. there hasn't been any kind of

missile strike in yemen in the last year and this one targeted american-born cleric anwar al awlaki. apparently, it just missed him. he is behind, they believe, the attempted christmas day bombing in 2009, inspired others. i would say he's number one on the hit list for america. he is considered the biggest threat to the u.s. homeland, just missed him. imagine, cynthia, what a great two-fer that would have been. >> it seems like the u.s. is sort of on a roll these days. what's going on? >> reporter: well, i think you will see that the u.s. is on a roll. obviously, we got bin laden dead now. but all of that intelligence they gathered from the bin laden compound is going to lead them to others. it's going to lead them to other al qaeda figures. they've got lots to work with now. i think in the coming weeks, you'll see a lot of drone strikes, a lot of raids wherever they can find people. >> as always, martha raddatz on top of the news. thank you, martha.

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>> announcer: "nightline" continues from new york city with cynthia mcfadden. >> well, they're some of the cutest creatures on the planet. tiny polar bear cubs, and they are almost never seen in the wild. there's good reason for that. the place where they are born happens to be extremely hot tile to humans, on the far northern canadian tundra, where temperatures run to the double digits below zero. neal karlinsky braved the elements for our series, "into

the wild." >> reporter: we've joined up with a small group of some of the world's leading wildlife photographers for the privilege of receiving something so rare, only a few hundred people on earth are believed to have ever experienced it up close. polar bear mothers taking their newborn cubs out into the world for the very first time. getting here isn't easy. a flight to winnipeg, followed by a small plane to churchill, manitoba, then a 2 1/2-hour train ride near the arctic, which ends nowhere near a station. here goes the train. we're in the middle of nowhere in the tundra, middle of the night and the train's leaving us here. another hour later, we're at a place called the wachee lodge. only open six weeks a year. there is no running water and space is extremely limited. inside, hard core wildlife

photographers from every corner of the globe. in the morning, they pile into vans converted with tank treads, hoping to find white bears hidden in white snow caves in conditions that can kill a person in minutes. >> got the tracks heading out. and then another set of tracks coming back in here. >> reporter: it's more than 40 degrees below zero. i'm wearing a ridiculous amount of clothing. and surrounded by people with fresh frostbite. as a native guide points out a set of unmistakable footprints. we're tracking a polar bear family. >> more than likely it's the same bear checking out the area here. we'll scope it out. >> reporter: on our first day, we spent eight hours staring at a hole in the snow. and then, just as a cold so pain ful came over, this. a living, brooefting stuffed animal-like cub poking his

little black nose out, playing an tumbling back inside. one you see them, they're like walking fluff balls. pure white, playing and climbing atop impossibly sleepy mothers. if you have ever seen pictures of baby polar bears this is almost certainly where they were taken. these baby polar bears. this is the first time they're seeing the sky. >> that's right. they are emerging from their den. she's introducing them to the world. and cubs are cubs. they're playful. they're running around, they're not listening to mother, naturally. they're enjoying themselves. they're experiencing the world for the first time. >> reporter: life long tracker morris spence finds the clues from the back of his snow mobile. and he has a face full of frostbite burns to show for it. you i have to say, you ride around on a snow mobile and your mustache is ice right now. >> yeah, it's always like that. >> reporter: there are certain spots, you know, that you see them making dens? >> not really. they're just a traveling bear.

when she stops, she'll stop and then they go again. >> reporter: we were incredibly lucky and found bears for four days straight. they travel to this exact slice of canada every november to bear their young, deep inside snow caves, emerging just before spring to make a 40-mile walk back to hudson bay, and the frozen water that will take them to their first solid food. are you not just astounded by this? >> i'm amazed. one of the most privileged people on the planet to be here. this is part of my job. very few humans actually get to be this close to a polar bear with its cub. >> reporter: pete ewens is here to study them. and he says climate change is depleting the sea ice these bears rely on to reach the only food on their menu. seals. how are the polar bears doing around here? >> these have the best studied bears on the planet. they're in decline. well over half of them will die

in the first year. and it's that critical survival of the cubs that determines your recruitment into your population. >> reporter: he says our trip matches the statistics. single cubs nearly ever day, from mothers who used to routinely have two. our last day would be the exception. suddenly, hours of breakdowns in the unforgiving tundra open up to yet another slumbering mother, but this time, with not one, but three cubs slowly waking up to play. as the wind kicks up, ice begins to form on some of the photographers eyelashes. they're freezing as they wait for the mother to make a move. when she does, watch the cub through the legs. did you catch it? one photographer did. the mother bear's hulking size seems to unravel as she suddenly climbs out, and with three little ones in tow, pushes on. the long walk of the polar bear,

including one cub, not much bigger than a poodle. just the kind of sighting to given even the skeptics hope. >> they are well inls lated. they have a great supply of warm milk and a beautiful mom. so, life's all good so far. >> reporter: in two years, these cubs will be on their own, and the cycle, in a part of canada that has the feel of another planet, will repeat itself as the polar bear's long journey marches on. i'm neal karlinsky for "nightline," near churchill, manitoba. >> certainly nice to watch from a warm place. a different kind of mother's day tribute. well, mother's day is, of course, sunday, which got us to thinking about the state of moth motherhood around here. and what we found out made us want to take a look at mother's day by the numbers. ♪ [ male announcer ] an everyday moment can turn romantic anytime.

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there is a lot to know about mothers. for example, what is the best place in the world to be a mother? you might be surprised at where the u.s. ranks. so, now, a look at motherhood, by the numbers. let's start with the best news out there for moms. though you may guffaw in disbelief. having kids may lower your blood pressure. the reason? motherhood provides a sense of purpose. and that puts the hassles of

life into perspective. except for those days when it doesn't. as for what moms themselves say they want, kids, you may want to rethink that box of chocolates or bunch of flowers. there are new hot gifts moms are looking for. according to a survey released this week, 62% of mothers said if they had the time and the money, they'd want -- cosmetic surgery. things like a tummy tuck or a breast lift. and guess what? mommy makeovers are on the rise. women had nearly 112,000 tummy tucks in 2010, up 85% in the last decade. breast lifts are, you should pardon the expression, up, 70%, in the same time period. a bit of not so good news for american moms. according to the 12th annual save the children index of the best place to be a mother, norway, australia, and iceland are in the top three spots.

the u.s.? a pitiful 31st of the 43 developed countries ranked. little surprise, maybe, that afghanistan ranks last. finally, we all know mothers are priceless. but if you had to put a dollar number on what she does, economists say, take the 14 different jobs she has, slug in the hourly wages posted by the bureau of labor statistics. jobs like chauffeuring, housekeeping and those delicious home cooked meals. $61,436 a year. doesn't sound like enough. happy mother's day, mom. well, if you'd like to post a video tribute to your very own mother, go to the "nightline" facebook page. that's it for our report tonight. tune in sunday for "this week". christiane amanpour will ask the president's national security adviser in the wake of osama bin laden's death how