captioning funded by cbs and ford. we go further, so you can. >> tonight, ukraine's foreign minister speaks frankly about his country's dangerous stare down with russia. in the early '90s when the soviet union broke up and ukraine became an independent country, you gave up your nuclear weapons. do you all look back on that and say, "it was a mistake." >> i do. >> do you feel that the united states owes you? >> partially. ( ticking ) >> someone is trying to send us a message that they can strike blows against us and we can't strike back. >> this former national security

official believes he was attacked in washington with a mysterious weapon. he's not alone. the director of the c.i.a. and the f.b.i. are investigating other incidents, two were reported at the white house. is the national security structure in danger of being incapacitated during a time of crisis? >> no, i don't think that's the case. >> but if people are being overcome on west executive avenue, is that an indication that the white house and its grounds are no longer safe? ( ticking ) >> i'm lesley stahl. >> i'm bill whitaker. >> i'm anderson cooper. >> i'm sharyn alfonsi. >> i'm scott pelley. those stories, tonight, on "60 minutes." ( ticking )

>> stahl: the threat of a russian invasion of ukraine keeps escalating, as last-minute diplomacy continues. president vladimir putin says ukraine belongs with russia, and wants a promise it will never join nato, the western military alliance. but his saber-rattling has produced exactly what he was trying to prevent: more nato and u.s. troops in eastern europe. still, yesterday, ukrainian president volodymyr zelensky angrily called on the west to do more, saying this is not about war in ukraine, this is about war in europe. today president biden met with the national security council at the white house, and secretary

of state blinken repeated the u.s. view that putin's plan to invade "is moving forward." we spoke late in the week with the foreign minister of ukraine, dmytro kuleba, about the crisis, at the front. >> dmytro kuleba: we still see a room for diplomacy to-- let's put it this way-- demotivate president putin from resorting to a large military operation. >> stahl: let me ask you about some hints that we've seen that your government is sending signals that you are willing to abandon your ambition to enter nato, in other words, to satisfy one of mr. putin's big demands. is that true? >> kuleba: no. we are not sending such signals. the majority of ukrainians want ukraine to become a member of nato. the only signal we are sending to the world is that if ukraine succeeds, and if russia pulls back, it will be much safer for entire democratic world.

>> stahl: are you facing any kind of pressure from the united states or any of the european nato members that you should loosen up on your insistence? >> kuleba: there are some countries who send us mess-- messages. and all i can say is that, again, ukraine is seeking membership in nato. >> stahl: has there been any subtle pressure from the united states for you to abandon your desire? >> kuleba: no. so far, this message is ca-- came from few european members of nato. >> stahl: is there a fear that this thing is widening beyond what's going on around your border? >> kuleba: this thing has been wide from the very beginning. it's not only about ukraine. it's a global-- it's about a global struggle between democracies and authoritarian regimes, between those who want to play by the rules and those who want to rewrite rules in their favor. >> stahl: you know, in the early

'90s, when the soviet union broke up and ukraine became an independent country, you gave up your nuclear weapons. you had a-- a giant arsenal, i think the third-largest nuclear arsenal in the world. you agreed to send the nukes back to russia. and in return, you got security guarantees from the united states and from russia. do you all look back on that and say, "we should not given up our nuclear weapons, it was a mistake?" >> kuleba: i do. >> stahl: do you feel that the united states owes you? >> kuleba: partially. you know, whatever mistakes were made in history, our current life gives all of us excellent opportunities to correct those mistakes. and given the fact that we abandoned our nuclear-- nuclear arsenal, given the fact that the security assurances that were

given to us failed, i think some countries should feel responsibility for this, and work hard on finding the right and efficient security guarantee for ukraine. >> stahl: yesterday putin watched test launches of russia's dreaded long-range nuclear missiles. ukraine faces an ever-tightening vise: russian forces continuing to advance from three sides-- choking ukraine like a boa constrictor, with tanks, fighter jets, and up to 190,000 troops; russian naval exercises in the black sea threatening a blockade, already disrupting commercial shipping. ukrainian soldiers and civilians are under intensifying shelling in the east. >> ben hodges: what a terrible shame that tens of thousands of people may die and-- and hundreds of billions of dollars

will be lost because of-- this ego. >> stahl: retired general ben hodges knows a lot about vladimir putin. hodges was a nato commander in 2014 when russia last invaded ukraine and annexed crimea. later, he was the top general of the u.s. army in europe until 2017. is putin boxed in at this point? >> hodges: no. >> stahl: well, if he withdraws... >> stahl: isn't he embarrassed? >> hodges: sure, but, i mean, that's-- that's-- i'm reluctant to say he's boxed in. this is a crisis 100% of his own making. >> stahl: yeah, but the world is going to say he was one-upped by biden. can he-- can he accept that? we know his ego. >> hodges: his ego should not be our-- our ultimate concern. our ultimate concern has got to be protecting the values that we care about. >> stahl: do you think what

happened in afghanistan, our ugly retreat from afghanistan, had any effect on his thinking? did he think the united states had become soft and weak? >> hodges: i think that the way we came out of afghanistan probably brought some satisfaction to president putin, to see us struggle like this. and i would imagine that in his mind he thought, "okay, this-- this new government doesn't have the strength to make hard decisions." so, i'm sure that that factored into his calculation. certainly a miscalculation-- nonetheless. >> stahl: you know, you have said that mr. putin could-- you used the boa constrictor analogy-- choke off ukraine without a full invasion. >> hodges: well, i was in kyiv just over two weeks ago and had the chance to spend about an

hour with president zelensky, and he really impressed on me the impact that his economy was feeling. there already was this pressure, the boa constrictor metaphor was already there. >> stahl: but if he can do that without a full-scale invasion, why would he move in? >> hodges: i don't think he is going to launch what some people call a full-on invasion, or all-out assault. i just don't think he needs to do that because he-- the continuous economic pressure could choke the government and cause it to collapse. >> stahl: to prevent that, the u.s. has sent in $650 million worth of military equipment, including javelin antitank missiles, large quantities of artillery and mortars, and secure radios. but washington is not sending troops into ukraine. foreign minister kuleba praised the biden administration's handling of the crisis. have they done enough?

>> kuleba: as long as russia sits on our border and in the occupied territories of ukraine, it's never enough. ukraine is not asking american soldiers to fight for us. this is our country and we will defend it, but, dear americans, what happens here matters to you as well, because if russia prevails here, other malicious powers across the globe will realize that the collective west is unable to defend its principles and what it stands for. and it will provoke them to act more aggressively in other parts of the world to pursue their interests against the u.s. interests. >> stahl: are you speaking about china? >> kuleba: i'm just speaking. >> stahl: do you think the united states should impose sanctions now? >> kuleba: it would be helpful to impose at least some.

>> stahl: there have been reports that your president, and perhaps you, have felt that the, president biden continually saying that an invasion is imminent, is boxing mr. putin in and perhaps almost encouraging an invasion. >> kuleba: no. we never-- we never thought that president biden is encouraging an invasion by russia, but we were very open with our friends in the united states that regular public messages about the imminence of war, they cause damage to our economy and to our financial stability. >> stahl: seems president biden got that message. this past week, he committed more help for the ukrainian economy. >> kuleba: they issue $1 billion in loan guarantees to ukraine. this is a message to everyone involved in business activity that partners of ukraine have

trust in this country, and they're confident that this country will remain stable, and it's safe doing business in this country. >> stahl: despite the hit to the economy, in kyiv, the capital, it's been looking like business as usual. just another european city, belying the drumbeat of war. at the center of the crisis is 44-year-old volodymyr zelensky on the frontlines in fatigues or dressed up with heads of state. he's an unlikely leader, a political neophyte who, less than three years ago, was a comedian on television. we talked about him with yale historian timothy snyder, author of several books on the region. this comedian, really, an entertainer gets on the world stage, and he's up against this powerful ex-k.g.b. agent who plays chess magnificently. he's never led anything before.

>> timothy snyder: that's true. this is, so to speak, a little guy, who's used to dealing with big guys, and who has found a way to do it, which is that he's a little funnier, he's a little faster, he's a little sharper. and, one thing for certain about him, is that he's not a product of a political machine. and that makes him a kind of wild card in this overall situation. but it is also what makes him intolerable for putin, because what putin wants is a predictable ukraine, a predictable ukrainian president, and zelensky, whatever his flaws, is the opposite of that. >> stahl: zelensky is ukraine's sixth president since it first became an independent democracy just 30 years ago. before that, says historian snyder, the country's suffering was pretty much unparalleled. >> snyder: ukraine is at the very center of the history of atrocity in the 20th century. it suffered more under stalin than any other part of the soviet union. and then it suffered more under hitler, along with belarus, than

any other place that the germans invaded. >> stahl: while the rest of the world is on edge, strangely, inside ukraine there's calmness. >> snyder: they are perfectly aware that there's a possibility of invasion, but the difference is that they don't think that this is so exceptional. they think it's come before and it can come again. >> stahl: if it comes again, and the russians invade, they'll face a ukrainian military that is far bigger, better-trained, motivated, and equipped than it was eight years ago when putin took crimea. >> kuleba: large-scale invasion in ukraine by russia will inflict huge damage on russia itself. economically, because of sanctions that will be slammed on russia immediately. militarily, because we are not the country that will give up. this is our land. we will be defending it. >> stahl: so, what happens if

this is the status quo? the russians have troops almost all around you. they're just sitting there, and they're hurting your economy. they're trying to suffocate you to the point that they can just get what they want from you. >> kuleba: well, you see, they tried to suffocate us, and destabilize us, and shatter us from the inside for the last 300 years. but they failed. i'm still sitting here with you as foreign minister of independent ukraine. we know the threat. we understand it. we learned how to live with it. and we stand for a just cause. ( ticking )

>> pelley: since 2016, u.s. government officials overseas and their families have reported

sudden, unexplained brain injuries with symptoms of vertigo, confusion, and memory loss. the c.i.a., f.b.i. and state department are investigating a theory that some of these officials were injured by an unseen weapon. who might be targeting americans, and why, are unknown. incidents have been reported in europe, asia, and latin america, but our reporting has found senior national security officials who say they were stricken in washington and on the grounds of the white house. the former officials you are about to meet are revealing their experiences for the first time. they were responsible for helping to manage threats to national security. >> olivia troye: i covered any and all emerging threats, homeland security incidents, domestically, so i covered whether it was from mass shootings to hurricanes, to natural disasters. >> pelley: olivia troye was

homeland security and counterterrorism advisor to vice president mike pence. she had served in the pentagon, deployed to iraq, served in the defense intelligence agency and the national counterterrorism center. at the white house, she worked in the 19th-century eisenhower executive office building beside the west wing. in the summer of 2019, she was descending these stairs toward the white house, when she felt she had been physically struck. >> troye: but it was like this piercing feeling on the side of my head. it was like-- i remember it was on the right side of my head, and i got like, vertigo. i was unsteady. i wa-- i felt nauseous. i was somewhat disoriented, and i was just, i remember thinking, "okay, you've got to-- don't fall down the stairs. you've got to find your ground again and steady yourself."

>> pelley: she steadied herself on a railing, but the "piercing feeling" continued, as she passed by this entrance to the west wing. >> troye: it was almost like, i couldn't really process. it was like a paralyzing panic attack. i've never had that. i've never felt anything like that. and so, i-- you know, i-- i thought to myself, "i mean, do i have a brain tumor out of the blue? is this what happens? am i having a stroke?" >> pelley: olivia troye was inside the security perimeter, headed to her car. she went down the steps, past the west wing, and down the closed parking lot, used by presidents, called west executive avenue. then she passed through the secret service gate and out to the staff parking in the ellipse, south of the white house. did you ever experience anything like this again? >> troye: so, not immediately. but i did again about a year later. it didn't happen on the steps.

it happened a couple times walking to my car on the ellipse. >> pelley: tell me about those times. >> troye: it was a similar sensation, but this time, it was very much the feeling of vertigo and dizziness. and i felt like i couldn't really walk. there was sort of-- it was like i had a depth perception issue, where i couldn't figure out where the ground was. and i would start walking, and i felt like i was just going to fall right into the ground. >> pelley: troye says she didn't report the episodes because she didn't want to believe she was seriously ill, and she worried what it would mean to her security clearance and career. after this interview, she reported for the first time. >> troye: there is a human aspect of it, of shame. and, do you really want to admit you're sick? do you want to come forward and tell someone that, especially as a member of the intelligence community? i think i'm still processing all of it, and thinking about, like,

how many more people are like me who felt this. >> pelley: it appears there are several. a senior member of the national security council says he was stricken in november 2020, on the same steps by the west wing. that former official, whose incident was first reported in the "new yorker," asked us not to name him. but he described the incident to a close colleague, john bolton, former national security advisor. >> john bolton: they had disorientation and ringing in their ears, and just a general inability to function. >> pelley: bolton told us, the official said he couldn't speak or think clearly. he was taken to an emergency room. the former official sent us this note, saying that, more than a year later, "i'm still recovering and suffering from headaches and other symptoms, and have been diagnosed with two other medical conditions that are believed to be the result of

the attack." he's still an outpatient at water reed national military medical center. >> bolton: that was a very debilitating attack, and similar to what others have reported. >> pelley: those "others" include miles taylor, also speaking for the first time. taylor was deputy chief of staff and, later, chief of staff of the trump administration department of homeland security. >> miles taylor: your job is to oversee the roughly 250,000 men adepa that conducted a range of missions, from aviation security to border security to cybersecurity. >> pelley: taylor told us he was hit with the same symptoms described by olivia troye. >> taylor: it was late one night in april 2018. i'd just become deputy chief of staff of the department, taking on some additional sensitive issues at d.h.s., and woke up in

my apartment that night, a row house on capitol hill, to a really strange sound. >> pelley: the sound that woke miles taylor is a common experience reported by dozens of americans stricken overseas. >> taylor: it was sort of a chirping, somewhere between what you would think is a cricket or sort of a digital sound. i didn't know what it was, but it was enough to wake me up. what was really strange about it is, i went to the window, opened up my window, looked down at the street. and, keep in mind, scott, this is probably 3:00, 3:30 in the morning. and i see a white van. and the van's brake lights turned on, and it pulled off and it sped away. >> pelley: how long did it last? >> taylor: this whole episode only lasted about seven to ten minutes. >> pelley: how did you feel the next day? >> taylor: off. off-- not ready to go to work, you know, kind of wanting to take the day off, you know, sick. >> pelley: then, about five weeks later, taylor says it happened again. >> taylor: next day, feeling off-balance, feeling just out of

it-- again, those sort of concussion-like symptoms you would have from, you know, getting knocked pretty hard in a sport. and that incident stood out to me, because i was actually just getting ready to leave to go to israel on a congressional delegation. we were going to meet the israeli prime minister, benjamin netanyahu, have some sensitive conversations with the israelis on important cybersecurity issues. and i remember because i got to the airplane at andrews air force base to take off and thought, "i'm already nauseous. i don't know if i can do this flight." >> pelley: both miles taylor and olivia troye became critics of the trump administration, but they told us that has nothing to do with what they see as a potential threat to national security. taylor says he became alarmed by that threat in 2018 after he heard of another case like his in the washington area. >> taylor: i became aware of a u.s. government official, more

senior than me, who'd experienced similar episodes at their place of residence. >> pelley: you say more senior than you. are you talking about a cabinet- level secretary? >> taylor: this was an individual that, yes, was roughly at the cabinet level in the trump administration, who had similar episodes occur. that, to me as a homeland security professional, was a big blinking red light. i mean, to me this said, "five-alarm fire." we may have ongoing activity targeting u.s. government officials here in our country. >> pelley: who was it? >> taylor: i can't say the individual out of respect for, you know, their privacy. i'll leave it at that. but someone senior enough to say, this is more than just a fluke. >> pelley: more than a fluke. a pattern, across two administrations. recent injuries among u.s. officials were reported in vienna, austria, ahead of a trip by the vice president to

vietnam, and in india, during a visit by the director of the c..a. in 2019, during a visit by president trump to london, two members of john bolton's national security staff became ill in a hotel. >> bolton: and that it was on the floor where we'd completely taken up with personnel from the white house and white house agencies struck me as being pretty good evidence of a deliberate attack. >> pelley: you believe it was an attack? >> bolton: i don't think there's any other hypothesis, when you begin to look at the number and the pattern that we've experienced. >> pelley: bolton says, months later, one of those staff members hurt in london said she was overcome, again, walking her dog in the washington area. we have found, she is not the only one who says they were attacked abroad and, later, at home. you must have thought that, when you were home in america,

that you were safe? >> robyn garfield: i'll tell you, when i landed from china, i literally was kissing the ground. >> pelley: we met robyn garfield in 2019. he's a commerce department official who told us that he, his wife, and two children were repeatedly hit in china. your daughter was literally falling down? >> garfield: yes, she fell down multiple times a day. >> pelley: they were evacuated, and enrolled in a state department treatment program at the university of pennsylvania. recently, garfield told us his family was hit again during their year of treatment in philadelphia. >> garfield: my wife catapulted out of bed and sprinted down the hallway to check the children, without any word. and she came back, and she told me that an extremely loud, painful, sound had woken her up. >> pelley: so, they moved to a hotel-- where garfield says it happened again.

>> garfield: and we woke up around, i believe 2:00 a.m., with strange vibrations in our bodies, and a sound. >> pelley: which led garfield to check on his children, in another room. >> garfield: i saw an extremely eerie scene, where both were thrashing in their beds-- asleep, but both kicking and moving pretty aggressively. and i went over to my daughter, and i put my head down next to her head, and i heard a very distinct sound, just right there, sort of like water rushing. so, i picked her up, took her and put her with my wife, and i came back and i checked my son. same sound, just right next to his head. so, i picked him up, put him on my shoulder, walked over to my wife, and i said, "we're getting out of here." >> pelley: garfield reported this to the f.b.i. today, his family is posted

abroad, where they continue to work to improve balance, eyesight, and memory. >> garfield: this is the most difficult aspect of this whole issue for me, are the children who've been impacted-- both mine as well as many others. i personally know the parents of, i believe, eight other children. i can tell you, i've personally seen balance issues in children that have never had that; trouble with finding their words, stuttering. and then, continuing challenges around vision. one of the things that we have heard from some parents is that these are manifesting in the classroom in real, tangible ways. >> pelley: persistent neurological symptoms are not the only fight these americans have faced. some of their earl reports were dismissed as psychosomatic, or illnesses connected to an infection or exposure to pesticides. some were told that they

were suffering the effect of old sports injuries. one theory had it that the sound these victims heard during the incidents was actually a particular species of cicada. >> unidentified person: it was rough. it was rough in the beginning. it was a dark place to be. we were kind of shoved aside, and they wanted it to go away. >> pelley: this man is among those who fought for recognition. he's one of the first cases, from 2016. americans assigned to the u.s. embassy in cuba say they and their families were struck at home, frequently, in the night. he remembers the first time. >> unidentified person: and that night, all the dogs started kicking off, in the neighborhood barking, which was very unusual for them all to go in chorus. and then this, just, loud sound, just absolutely filled my room. it felt like my head was slowly starting to get crushed. >> pelley: we agreed not to use his name. he is not allowed to say what federal agency he worked for.

>> unidentified person: and then the severe ear pain started. so, i liken it to, if you put a q-tip too far and you bounce it off your eardrum. well, imagine taking a sharp pencil and just kind of poking that. it was very jarring and painful. and eventually, i started blacking out. ( drum ) >> pelley: with the first public reports coming from cuba, the affliction became known as "havana syndrome." more than two dozen embassy officials reported injury, but an early f.b.i. report speculated it was all mass hysteria. his brain injuries left him disabled, essentially retired, at the age of 36. a weighted vest helps him balance. his service dog helps with walking and his loss of vision. legally blind in one eye? >> unidentified person: correct. yeah. >> pelley: what have the doctors told you? >> unidentified person: it's not the eye, it's the wiring. >> pelley: what do you mean? >> unidentified person: the eye function, as itself, is

completely correct and appropriate. it's the signal that comes out the back of the eye into the brain, is where the problems are, and no one really knows how to fix that. >> pelley: he is speaking tonight, for the first time, to put an end to doubt. you have not wanted to do this interview. >> unidentified person: no. this is probably one of my worst nightmares. >> pelley: why is that? >> unidentified person: i didn't do my job because i want to be known. i did my job because i love my country. and i was good at it. god, and i miss my job. i'm here because i'm tired of the gaslighting that keeps happening from the u.s. government. i'm tired of this yo-yo-ing. because i'm watching new colleagues, and friends that i've trained with, and friends that i've known for years, that are being sent to these countries and coming back a shell of their former selves. we need to help them, and we need to stop this. >> pelley: but, who is it that must be stopped? when we come back, we'll ask the

director of the c.i.a. about his investigation, and we'll look at the kind of device capable of inflicting brain injury without a trace. ( ticking ) [ doorbell rings ] oh! there's my little nephew. he looks more like dad every time i see him. -dad is old. -right. so, your message said you wanted to talk about insurance? i said, "i want you to talk about insurance."

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>> pelley: brain injuries suffered by u.s. officials in washington and abroad are the focus of an intense investigation. after starting with around 1,000 possible cases, a c.i.a. task force has zeroed in on about two dozen that cannot be explained.

the task force, which includes the f.b.i., is led by a c.i.a. officer who helped find osama bin laden. the new director of the c.i.a., william burns, told us, one thing is already clear-- after early disbelief, these injured americans can no longer be doubted. >> william burns: in my first week as director, i began what has become dozens and dozens of meetings with affected officers and family members. and i found their stories to be powerful and compelling, and sometimes heartbreaking. >> pelley: bill burns had heard those stories from c.i.a. officers who reported injury since 2016, but this past fall, while on an official visit to india, a member of his staff was stricken in their hotel. later, burns personally escorted that staff member to medical evaluations. it seems that the delhi incident might have been intendo

>> burns: i don't know. and as i said, i can't comment on individual cases here as well. all i can tell you is that each story i've heard, each officer i've met with, who's been affected by this, just redoubles my commitment and my determination on this issue. i have enormous faith... >> pelley: bill burns served five presidents at the state department, rising to the highest rank in the foreign service. he took over c.i.a. for president biden last spring. >> burns: early on, i tripled the number of full-time medical personnel working on this issue. we streamlined access to walter reed, established new partnerships with other world-class medical providers, increased the number of case managers, and we're also making progress on the investigative side as well. >> pelley: progress on the investigative side came, this t noh, with a report on the>>r.e >> pelley: dr. david relman helped lead two government panels that investigated the injuries.

he's a professor of medicine at stanford university. >> relman: what we found was, we thought, clear evidence of an injury to the auditory and vestibular system of the brain. everything starting with the inner ear, where humans perceive sound and sense balance, and then translate those perceptions into brain electrical signals. >> pelley: dr. relman's committees focused on one subset of patients whose experiences seemed inexplicable. >> relman: this subset of cases had a very unusual, so-called acute sensory event, an experience that consisted of the abrupt onset of intense pressure or vibration in the face or head, sometimes with the abrupt onset of sound. >> pelley: sound, like that

described by the officials who spoke to us. >> unidentified person: and then this, just, loud sound just absolutely filled my room. >> pelley: this former official, who we agreed not to name, recorded the sound at his home in havana. before we play it, understand that the sound does not cause the injury. it is a byproduct-- like the sound of a gun, which is not what does the harm. here's what he recorded. ( tone ) >> pelley: the injured officials we spoke with said the sound, or a feeling of pressure, came from one direction, and focused in one location. >> taylor: it was a continuous sound, and one that only changed based on my location. >> relman: they left, it dissipated. they returned, it recurred. that to us was something that we had never heard of, we could

not explain by known medical or environmental conditions, and to us, deserved our special attention in an effort to understand what might be the plausible mechanism. >> pelley: that mechanism, dr. relman's committees concluded, was most likely "pulsed electromagnetic energy." in other words, a focused beam of microwaves fired from a distance. >> james benford: i think the best explanation, the most plausible, is that it's a high-power microwave weapon. >> pelley: james benford is a physicist and leading authority on microwaves. he was not part of the government studies, but he co-wrote the book on microwave transmission. these are portable microwave transmitters of the kind that could damage the tissues of the brain. >> benford: there are many kinds, and they can go anywhere in size from a suitcase all the way up to a large tractor- trailer unit. and the bigger the device, the longer the range.

>> pelley: this would be able to transmit its microwave energy through the wall of a van, the wall of a home, something like that? >> benford: vans have windows. microwaves go through glass. they go through brick. they go through practically everything. >> pelley: the technology, benford told us, has been studied more than 50 years. >> benford: it's been developed widely in, perhaps, a dozen countries. the primary countries are the united states, russia and china. >> relman: the implications of a mechanism like that suggest something different about the world now, involving the loss of norms. humans were affected in a serious fashion, and for that very reason alone, we have to understand this better. >> pelley: the investigation is also trying to understand who could be behind this, and their motive e a ol for spies. some devices are capable of

collecting data, remotely, from phones and computers. whatever is causing the brain injuries, a c.i.a. interim report last month said, there is no evidence of a massive, global campaign to attack americans. the interim c.i.a. report last month said, "we assess it unlikely that a foreign actor, including russia, is conducting a sustained, worldwide campaign harming u.s. personnel with a weapon or a mechanism." do you mean to say that no one was harmed by a hostile actor? >> burns: not at all. the inteligence community assesses now that there's not a single cause that it would explain the more than 1,000 incidents that have been reported since havana in 2016. we've also not yet been able to link a foreign state actor or an external device or mechanism to any of those cases. >> pelley: this is the world's

preeminent intelligence agency. why is this so hard to figure out? >> burns: it's a very complicated issue, you know, dealing with a whole range of incidents which have, you know, different kinds of explanations for them as well. it's a very charged issue, emotionally, as well. i understand that very clearly. and that's what, you know, makes me even more determined not only to ensure people get the care that they deserve, but also that we get to the bottom of this. >> pelley: former national security advisor john bolton fears there is a threat to the highest levels of government, given the two national security officials who say they were overcome on west executive avenue by the west wing inside the white house gates. >> bolton: if we were at war and an adversary could disable the president and his top advisors, or commanders in the field, it could render us extraordinarily vulnerable. we don't know that that's the threat we're facing. but, i would much rather focus

on finding out the answer now, rather than finding out later when it may be too late. >> pelley: former homeland security chief of staf miles taylor says he believes he was targeted in two mysterious incidents at his washington home. >> taylor: someone is trying to send us a message, that they can strike blows against us and we can't strike back. that line being crossed into the united states takes this in some ways just shy of the realm of warfare. >> pelley: is the national security structure in danger of being incapacitated during a time of crisis? >> burns: no, i don't think that's the case. >> pelley: but if people are being overcome on west executive avenue, is that an indication that the white house and its grounds are no longer safe? >> burns: no. i don't believe that's the case. what it is an indication of, is that we need to take each of these reported incidents very seriously. and as a government-- and this

is a government-wide effort-- to pour the very best resources we have into this. >> pelley: what line is crossed if a hostile actor is doing this in washington, d.c.? >> burns: oh, that-- that would be a pretty profound line to be crossed, if in fact that were the case; if we were ever able to develop concrete evidence that that were the case. but we do not have evidence of that at this point. >> pelley: you understand how frustrating your comments must be to some of these people who believe they know exactly what happened to them, on what day, and at what time, and what happened to their children-- and yet, the director of the c.i.a. is saying, we can't connect the dots; we don't know enough yet. >> burns: we're not at a position yet where we can offer hard evidence that would connect all those dots. but as i said, we're not done yet. we still have a lot of work to do. and what i've said directly to a number of those officers is, my promise is that i am absolutely

committed to exhausting every alternative, so that we can provide the kind of answers that we owe them. >> pelley: this past summer in geneva, president biden raised the issue with russian president putin. the russians deny they're involved. the secret service declined to comment on white house security. the iron gates of west executive avenue, by the west wing, went up in 1951 after the attempted assassination of harry truman. 70 years later, there is evidence the gates may have been breached by an invisible threat. ( ticking ) >> the youngest victims: stories of children believed to be affected by havana syndrome, at 60minutesovertime.com, sponsored by cologuard. fries or salad?

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( ♪♪ ) (chiming) ( ♪♪ )

(laughter) ( ♪♪ ) >> pelley: i'm scott pelley. we'll be back next week with another edition of "60 minutes."

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