Episode Description

Klári arrives in Princeton just as war breaks out in Europe.

With John von Neumann absorbed in work, Klári struggles to find a niche in her new suburban home while dealing with devastating losses. A new chapter opens for Klári when the U.S. finally enters the war and women are called into the workforce.

Atomic bombing of Japan
ENIAC Operators

Episode Transcript

Episode 2: Women Needed

KATIE HAFNER: Before we get into it, just a note—this episode includes content that could be upsetting. It makes reference to violence, depression, self-harm, and loss.

ASHRAYA GUPTA: It's funny thinking about Klara's description of this town. Cause I feel like looking around on this, like, sunny day, it looks…

SOPHIE MCNULTY: Picturesque.


KATIE HAFNER: The voices you’re hearing belong to two of our producers, Sophie McNulty and Ashraya Gupta. They’re in Princeton, New Jersey on their way to Klára von Neumann’s first home in the United States.

GPS: In 1000 feet, your destination will be on the right.

ASHRAYA GUPTA: Oh, here it is.

SOPHIE MCNULTY: Oh, Westcott Road. Oh my goodness.

KATIE HAFNER: Sophie and Ashraya pull up to Klári’s house.

SOPHIE MCNULTY: Let's knock on the door. Oh boy. This is definitely an adventure.

KATIE HAFNER: I’m Katie Hafner, and this is Lost Women of Science. This season is about Klára Dán von Neumann, who wrote some of the earliest lines of computer code, back when a computer was the size of a Manhattan studio apartment.

And in this episode, we chart the course of the second World War– the horrors that unfolded, the opportunities that arose, and what this all meant for Klári von Neumann.

In the first episode, we met Klári, the self-described “grasshopper in very tall grass,” always on the hunt for new and better horizons. She fell in love with the mathematician John von Neumann and married him. When we last left her, she was sailing to her new life with him here in Princeton.

So after all that running around–from the casinos of Monaco, to blowout parties in Budapest, and from one husband to another… to another… Klári finally arrived in Princeton for good on September 5th, 1939, four days after Hitler had invaded Poland, starting World War II. And suddenly…there she was. In her new life, with her new husband.

On an immigration document, she listed her profession: housewife. And her place of employment? 26 Westcott Road, Princeton, New Jersey.

SOPHIE MCNULTY: Hi. This is super random. I'm so sorry to interrupt you. Um, but we're doing, we're doing a podcast on Klára Von Neumann. Did you know that she used to live here?




KAREN REID: I did because my in-laws actually bought the house from John von Neumann’s widow.


KAREN REID: My husband's family has been here since 1957.

KATIE HAFNER: That’s Karen Reid– she offers to give Ashraya and Sophie a tour.

Not only does she know that Johnny and Klári used to live in her house–in a way, they still do…Karen’s son’s bedroom used to be Johnny’s office.

KAREN REID: And every time he was struggling with math, I said, how could you be struggling in math? This is, come on, there's gotta be some aura in these walls.

KATIE HAFNER: And it turns out that in the last 70 some-odd years, the house has stayed pretty much the same. A few bathrooms, the kitchen…they’ve been remodeled. But the rest is just as the von Neumanns left it…It’s beautiful–it has old windows with rippled glass…

KAREN REID: I mean, these are all original windows.

KATIE HAFNER: A big living room that Klári and Johnny used for their frequent and famous cocktail parties…

ASHRAYA GUPTA: Large enough to accomodate 20, 30 couples for dancing.

KATIE HAFNER: A study with built-in bookshelves, which of course didn’t contain enough space for all their books…

KAREN REID: Yeah, but obviously the bookcases are all the same and—

KATIE HAFNER: But, as Sophie and Ashraya head back to the car, they start imagining what it was like for Klári to move here in 1939, just as World War II began, and they’re struck by something.

SOPHIE MCNULTY: There's like a quietness about that house.


SOPHIE MCNULTY: And I guess like coming from where she came from, like this crazy huge family...

ASHRAYA GUPTA: A city and a house that had three generations in one house…You go from one floor to the next and you just have other people that you can interact with. It’s so different.

SOPHIE MCNULTY: Yeah. It's this huge built-in network of people there to like, support and love you. You just, it’s like all you have here is John. And John's so busy, right? You're just on your own a lot in a lot of ways. And she doesn't seem like someone who liked to be alone.


GEORGE DYSON: I think she didn't know what to make of it. I think it was very hard on her.

KATIE HAFNER: That’s George Dyson, the science historian you met in the first episode.

GEORGE DYSON: Princeton had this sort of, this pigeonhole for faculty wives, they just were supposed to go to the certain parties and behave in a certain way. And Klári, of course, would break that mold.

KATIE HAFNER: Klári was a faculty wife because in 1939, Klári’s first year in Princeton, Johnny was working at the Institute for Advanced Study, which is where Sophie and Ashraya go next.

CAITLIN RIZZO: There’s actually skating on the pond.


KATIE HAFNER: That’s Caitlin Rizzo, the archivist at IAS. She’s pointing to a pond on the Institute’s 800-acre campus.

SOPHIE MCNULTY: I’m just thinking, like, what a beautiful, calm place to work.

ASHRAYA GUPTA: I know. It’s like. I feel like it's exactly the setting for what they wanted it to be.


KATIE HAFNER: The founders envisioned the Institute as a place for scholars to do their work in a frictionless bubble.

The Institute’s permanent faculty were well-paid, well-housed, and at liberty to explore the ideas they wanted to work on. Kind of like a MacArthur genius grant for life. Everything about the Institute was designed to give its scholars a good life – beautiful grounds, well-appointed libraries, access to assistants and secretaries. Basically all the scholars were men. At the time, there was only one woman, Hetty Goldman, an archeologist. And while the scholars got ample resources, this was not the case for their wives…

CAITLIN RIZZO: That infrastructure didn't exist for the women. And, you know, early on everything on campus is planned around, you know, this person is lecturing. This person has a seminar at Fine Hall. And the women are kind of seen as an accessory, no matter how intelligent they are.

KATIE HAFNER: Klári wasn’t an exception. Without her usual anchors, all she wanted was some familiarity. Or at least a nearby watering hole.

KLARA VON NEUMANN: But this was not to be.

KATIE HAFNER: Here’s Eva Szabo reading from Klári’s memoir.

KLARA VON NEUMANN: There are no small, smoky, intimate bars in Princeton.

KATIE HAFNER: On top of the sheer culture shock, Klári had to figure out how to be Mrs. John von Neumann, part two. And the vestiges of Johnny’s first marriage were still very much in the picture: Johnny’s ex-wife and his four-year-old child.

MARINA VON NEUMANN WHITMAN: Looking back, I’m sure that Klári found me difficult and somewhat intimidating.

KATIE HAFNER: That’s Marina von Neumann Whitman, Johnny’s daughter. She lived with her mother, Mariette, at the time, but the two of them were constant fixtures in Klári’s new life.

Klári was especially bothered by Mariette, Johnny’s ex-wife.

MARINA VON NEUMANN WHITMAN: I think she was aware of and doubtless troubled by the fact that my mother and father, long after they were divorced, maintained this kind of flirtatious relationship with each other.

KATIE HAFNER: Even after she left him, Mariette sent Johnny letters with “Million kisses” in the sign-off, or questions like “Do you love me a bit?”

MARINA VON NEUMANN WHITMAN: Drove her nuts. Why wouldn't it?

KATIE HAFNER: When she first arrived in the U.S., Klári did have at least one comfort:

her recent rescue mission to get her family, and Johnny’s, out of Europe meant that her closest relatives had escaped the worst of Nazi persecution. But they were now immigrants, transitioning to a totally new culture, uncertain they’d ever be able to return to their old life.

Klári was part of a big Jewish family, and that family had borne the weight of antisemitism in Europe. Like many Jews in Europe, Klári and Johnny had both converted to Catholicism, but that wouldn’t have protected them had they stayed. They were probably both haunted by the horror they were watching unfold back home, and, perhaps, they both felt guilty over getting out when others didn’t.

GEORGE DYSON: But I mean, how do you deal with, you come to this great life in America, but nine out of ten of your relatives die in, you know, the Holocaust.

KATIE HAFNER: Klári’s father, Charles Dán, took the transition especially hard, grieving the loss of everything he’d known. As Johnny put it to Klári in a letter at the time…

JOHN VON NEUMANN: He is going through…the process of tearing himself off from his country, his factory, his life. I imagine that this, at the age of over 60, is a trauma!

KATIE HAFNER: And in December that same year…1939…

ANANYO BHATTACHARYA: Tragedy strikes within a few months.

KATIE HAFNER: That’s Ananyo Bhattacharya, who just published a biography on John von Neumann titled The Man from the Future. Charles Dán, Klári’s father…

ANANYO BHATTACHARYA: …who's used to being, sort of, a man of wealth and influence in Hungary, suddenly finds that he's unable to adjust to his new life and a week before his first American Christmas, he ends his life by stepping in front of a train.

KATIE HAFNER: In her memoir, Klári discusses important events and people in her life with seemingly remarkable candor –two failed marriages, her difficult immigration, the war. But the drafts we’ve seen don’t include one word about her father’s suicide.

MARINA VON NEUMANN WHITMAN: Things like that were a deep, dark secret in those days.

KATIE HAFNER: There’s really no way to know what this loss meant to Klári, except to imagine. And it’s not hard to imagine that for someone not at all yet rooted in a new environment–for anyone, really–this loss was completely devastating.

MARINA VON NEUMANN WHITMAN: She was her father's favorite, so I assume it affected her particularly.

KATIE HAFNER: And the world around her didn’t offer much relief. Glued to the radio, Klári and Johnny witnessed, day by day, the devastation of their homeland.

ARCHIVAL TAPE: It was about dawn this morning that the first reports came in…

ARCHIVAL TAPE: Denmark submitted without a struggle as Nazi Germany…

PRESIDENT FRANKLIN D. ROOSEVELT: There is no demand for sending an American expeditionary force outside our own border…

ARCHIVAL TAPE: After six weeks of total war, France has signed a separate armistice with Germany and Italy. Her troops were outnumbered…

KATIE HAFNER: But for now, that war was on the other side of an ocean. Here’s George Dyson again.

GEORGE DYSON: The other thing to remember is how late it was that the United States came into the war, which was driving all these Eastern Europeans nuts, because their people are being exterminated. And the United States will still not enter the war.

KATIE HAFNER: Johnny, for one, was urging the U.S. to go to war.

In Klári’s words, he was an “ardent interventionist” — others called him a straight-up hawk.

GEORGE DYSON: People like von Neumann, and a lot of these physicists, were putting stuff in place. So when, when war was declared, they would get involved.

KATIE HAFNER: And in December of 1941…

ARCHIVAL TAPE: We interrupt this program to bring you a special news bulletin. The Japanese have attacked Pearl Harbor, Hawaii by air, president Roosevelt has just announced.

KATIE HAFNER: The U.S. finally went to war. And Johnny disappeared into his work, leaving Klári on her own, with a lot on her mind and not enough distractions.

AGI ANTAL: She feels that in Princeton, they don't regard her as a talented, brilliant woman.

KATIE HAFNER: That’s Agi Antal, one of our Hungarian translators. You met her in Episode 1. She read all of Klári’s letters from this period that we found at the Library of Congress. In one letter, Klári writes that Princeton sees her as pretty enough, but otherwise …an average woman…

AGI ANTAL: …from whom they cannot expect anything special, and the best would be if I gave birth for a kid. Otherwise I would be very bored there.

MARINA VON NEUMANN WHITMAN: I think it was sad that she never had children of her own.

KATIE HAFNER: At the Library of Congress, in a sea of bureaucratic-looking letters, I came across an unexpected document – it looked like a diploma of some kind. But I quickly realized it was something else: a certificate of cremation. It wasn’t set apart in any way – just thrown in there with the rest. The gothic type is large. It’s dated June 16, 1942, and where one would expect to see a name, there’s just “Baby Girl von Neumann.”

Klári was pregnant in the early days of the war. She and Johnny seemed to be excited. In a letter Johnny wrote to a friend at the time, he signed it: “Best greetings from both of us, and 1/2 (squared).”

But, because Johnny was away doing war work, Klári was alone for much of the pregnancy. She had to look after herself and the house. In June of 1942, she had a late-term miscarriage.

MARINA VON NEUMANN WHITMAN: And somehow she blamed it on my father for her opening the heavy garage door. This is all very piecemeal in my head.

KATIE HAFNER: Who knows what really happened. What is clear is that Klári was suffering at her housewife post. She was dealing with heartbreaking losses and struggling to find an outlet for her intellect and energy.

But with men leaving for the war abroad, this was about to change.

ARCHIVAL TAPE: Millions of women who have never before been employed in industry… they’re stepping in wherever they’re needed to do a man’s job…

ARCHIVAL TAPE: Women are called upon to leave their homes and take jobs.

KATIE HAFNER: Coming up, Klári gets to work. I’m Katie Hafner, and this is Lost Women of Science.


LEANN ERICKSON: One of the most interesting things that I found in my research was the classified ads.

KATIE HAFNER: That’s LeAnn Erickson, a filmmaker whose documentary Top Secret Rosies follows the work of female mathematicians during World War II.

LEANN ERICKSON: And the female jobs before the bombing of Pearl Harbor were things like cook, cleaning lady, maybe a teacher. And immediately, and I mean immediately after Pearl Harbor, when I started looking at the Philadelphia Inquirers, they're looking for female mathematicians, female engineers.

KATIE HAFNER: And Klári, like many women in America, got one of those homefront jobs.

ANANYO BHATTACHARYA: Klára Dán has spent some of the war years doing, um, her own war work at Princeton, the office of population research.

KATIE HAFNER: That’s Ananyo Bhattacharya again.

ANANYO BHATTACHARYA: And what they're involved in doing is demographic projections, looking at the shift of post-war populations and projecting all of that into the future. And she seems to have been extremely good at it.

KATIE HAFNER: Klári started the job in February of 1943. After dealing with the tragedy of losing a child, and the monotony of domestic life, her life suddenly looked a whole lot brighter.

KLARA VON NEUMANN: At long last my old dream has been fulfilled, I am so busy that the twenty-four hours of the day could be doubled and I still would not be able to do everything I would like to.

ANANYO BHATTACHARYA: And she actually gets promoted and turns down an offer of an academic post in 1944.

KATIE HAFNER: Johnny makes a big deal of this promotion in his letters to Klári. He’s so proud of her. He tells her that it takes most people six to eight years to get an offer like that. He assumed she’d do it in three, and here she is, just a year and a half into the work, with a new fancy job on the table.

But, Klári, who held only a high school degree, still doubted her own talent.

ANANYO BHATTACHARYA: You know, Klára is quite insecure and often terribly modest about her own abilities, particularly her own mathematical abilities, but that's extremely difficult to believe given how successful she was.

KATIE HAFNER: Her official job title was “Head of Statistical Computing Group” at Princeton University. And so Klári entered the field of computing. But she still wasn’t exactly working with computers…at least not yet.

CLAIRE L. EVANS: For close to 200 years a computer wasn't a thing. A computer was a job, as in someone who computes, who performs computations for a living. And it was a job that was conducted by and large by women.

KATIE HAFNER: That’s Claire L. Evans, the author of Broad Band, a history of women in computing. At Princeton, Klári’s statistical work probably looked a lot like this human computing that Claire is talking about.

CLAIRE L. EVANS: It was doing these unglamorous, tedious smaller calculations that essentially served as, you know, the underlying computational infrastructure of the early scientific age.

KATIE HAFNER: In the past, human computers had charted the skies and helped sailors navigate. And now, they turned their attention to war. Some divisions calculated where and how to fire weapons…

CLAIRE L. EVANS: They were doing these, uh, differential calculus equations that were designed to calculate ballistics trajectories.

KATIE HAFNER: Others, like Klári at the Office for Population Research, did more theoretical work. Let me be clear: this was not a job that anyone could do–you needed real math skills. With the war on, the unglamorous job of human computing was in high demand and for the women doing the work…

LEANN ERICKSON: It was an amazing advantage for them.

KATIE HAFNER: That’s Leann Erickson again.

LEANN ERICKSON: And they immediately not only had this high level job, but also probably double the money they would have made in any other female kind of role that they could have had pre-Pearl Harbor.

KATIE HAFNER: It must have been intense– working 16-hour days with a team of other women.

And for the women LeAnn interviewed, their work also left them with a lifetime of lingering ethical questions. Some didn’t even tell their children about what they did until years later.

LEANN ERICKSON: As I did the project, I started to realize the emotional burden that these women carried. They were torn, knowing what was happening in Europe–if they could help in some way, it was that they were helping with their mathematical skills to create these ballistics tables. But then on the flip side, what they're doing with their math skills is making sure that every bullet, every bomb is deadly–is accurate, hence deadly.

KATIE HAFNER: In the hurried fog of war, there wasn’t time to stop and reflect on the implications of what they might be doing.

The work was feverish. The women, under intense pressure. It was clear they needed new ways to speed up the math.

This is where computers, as they are known today, enter the story.

At certain computing divisions across the country, mechanical calculators and rudimentary computing machines were brought in to accelerate calculations needed for the war.

Human computers helped operate them.

This was the start of the modern computer age. The machines that were built in the next few years would change the course of history. They would also come to dominate Klári’s postwar life.

I got to see an example of a precursor to the digital age at the Computer History Museum in Mountain View, California.

KATIE HAFNER: It is, it looks like somebody's insane work bench.

KATIE HAFNER: The machine I’m looking at is called a differential analyzer. Here’s senior curator, Dag Spicer.

DAG SPICER: Well, a differential analyzer was a, originally quite a large, almost room-sized mechanical contraption…And it was really about gears and wheels and shafts and pulleys.

KATIE HAFNER: What might take a human computer 20 hours with a desktop calculator could be cut down to 15 minutes with the differential analyzer. But it wasn’t exactly convenient.

LEANN ERICKSON: The problem with the mechanics of this is that the differential analyzer, the longer it ran, the more it shifted out of whack. And then the equations got worse and worse and they were no longer accurate.

KATIE HAFNER: That’s LeAnn Erickson again.

LEANN ERICKSON: It was constantly something you'd have to test by doing hand calculations against what the machine was doing.

KATIE HAFNER: So there was a lot of interest in developing better machines to speed these calculations up.

And this brings us back to Johnny and the work he was doing in the early 1940s.

Throughout the war, while Klári was in Princeton, Johnny had been crisscrossing the country, on a mad dash to find the best new technology. He visited Harvard, where a computer called the Mark I used paper-tape to churn out calculations. He went to Bell Labs, where a whole series of new computer designs were being tested. And then, at the University of Pennsylvania, he saw the ENIAC, an early electronic computer that moved with remarkable speed.

And why was he so determined to find new powerful machines? It had to do with creating new powerful weapons. And this, in turn, had to do with Project Y, a government laboratory Johnny had joined in 1943.

NIC LEWIS: It was a top secret project during World War II to build an atomic bomb before Nazi Germany could do the same.

KATIE HAFNER: That’s Nic Lewis, a historian of technology at Los Alamos National Laboratory. The work at the lab was completely classified. Los Alamos remains a center of government research today–and it still has some pretty strict policies on communication.

NIC LEWIS: I'm recording at home today because we can't have personal electronics in our offices.

KATIE HAFNER: So, while Nic couldn’t give us a tour of the lab itself, he walked us through its history. During World War II, Los Alamos was the site of Project Y, one of several arms of the Manhattan Project. It attracted many of the world’s top minds, a disproportionate number of whom were Hungarian.

Johnny compared Los Alamos to the moon. In 1943, he wrote to Klári:

JOHN VON NEUMANN: The atmosphere is thin…the whole place queerer than I can describe.

KATIE HAFNER: But while he could tell her about the landscape, he couldn’t describe the work he was doing–at least not in letters. The lab was focused on designing a bomb. In the 1940s, most of the atomic bomb technology was completely new. And the materials were expensive…

NIC LEWIS: They couldn't just conduct experiments. It would waste material and it would take a lot of time. So the theoretical division at the very beginning had to use computation.

KATIE HAFNER: Project Y’s theoretical division, or T division as it was called, was responsible for researching weapons–not with physical material, but with computation. And so, as Johnny explained to Klári in a letter:

JOHN VON NEUMANN: By the way: computers are, as you suspected, quite in demand here too.

KATIE HAFNER: More often than not, these human computers were women. And just like in other divisions across the country, the sheer volume of calculations was just too much.

NIC LEWIS: So the lab brought in a collection of IBM punched card accounting machines.

KATIE HAFNER: These were early digital electromechanical computers–a step up from the analog differential analyzer I saw at the Computer History Museum.

NIC LEWIS: And this was really a labor saving effort to let the human computers work on the difficult problems, the machines would take over the simpler, but really tedious problems.

KATIE HAFNER: In a way, the punch-card machines were pretty incredible employees– they sped up calculations by a lot, not because they were faster than the humans–they weren’t really. What they could do was work 24 hours a day. But these machines were by no means perfect–they could do only relatively simple math, and they still relied heavily on human operators.

And so, human computers were still essential at Los Alamos. And their work was in high demand.

At this point in the early 40s, Klári was still performing computations for the Office of Population Research in Princeton, a world away from Project Y. But Johnny was keeping tabs on her work from afar…


KATIE HAFNER: When Klári complained to Johnny about her job, he urged her to quit and take college classes. He even gestured to future computing opportunities where he was in Los Alamos.

JOHN VON NEUMANN: And remember, they would probably take you here in no time.

KATIE HAFNER: At this point in their letters, they start throwing around the idea of teaming up…

JOHN VON NEUMANN: You told me…that you might want to collaborate with me.

KATIE HAFNER: This wouldn’t materialize for several years. In fact, they wouldn’t join forces until after the war.

And why? It might have to do with the nature of Los Alamos itself. Project Y was shrouded in secrecy. In fact, most of the scientists at Los Alamos were stuck there. Johnny was one of the few people–maybe the only person– who could leave. He was granted this special permission since his brain was needed elsewhere to advance the very work he was doing in Los Alamos. And, to boot, his wife lived and worked in Princeton.

According to Klári’s memoir, Johnny was reluctant to bring her out west, for fear that he’d risk losing his hard-won commuter status. And apparently, Johnny did not do well confined to one place…

And so, for the time being, the partnership was put on hold. Klári would stay in Princeton. And Johnny, on the road.

Back at Los Alamos, bomb development was well under way. But, even with training in physics or mathematics, the human computers at Los Alamos were often left in the dark. Nic Lewis describes how one of those human computers talked about it years later…

NIC LEWIS: She said that she had no idea what the lab was working on aside from something powerful. She was never told and said she never asked what was happening until after Trinity.

ARCHIVAL TAPE: Bombs away, bombs away…

KATIE HAFNER: The Trinity Test took place before sunrise on July 16th, 1945 in the middle of the New Mexico desert.

Though they had a hunch that something unusual and important was happening that day with all the important scientists gone, and though a flash was visible through much of New Mexico, most of the computing division still didn’t know that the U.S. had successfully detonated the world’s first atomic bomb.

We don’t know what Klári was told about Trinity. However, three days after the detonation, Johnny wrote to her. He’d been at the test site.

JOHN VON NEUMANN: I was away for 36 hours, but slept it off – life is exciting.

KATIE HAFNER: Perhaps for Johnny, all that mattered was the thrill of scientific discovery, or the assurance that the U.S. had developed nuclear capabilities before the Germans did.

NIC LEWIS: He didn't seem to have too much compunction against the development of atomic or thermonuclear weapons.

KATIE HAFNER: Less than a month after Trinity, the public would finally learn about these horrific bombs.

On August 6th, 1945, the U.S. dropped an atomic bomb called Little Boy over the city of Hiroshima, instantly killing about 80,000 people, most of them civilians.

Three days later, the U.S. dropped a still more powerful atomic bomb, called Fat Man, over Nagasaki, instantly killing another 40,000.

PRESIDENT HARRY S. TRUMAN: We shall continue to use it until we completely destroy Japan’s power to make war.

KATIE HAFNER: In the months that followed, countless others died from burns and radiation sickness. And over the years complications from radiation exposure caused the incidence of cancer, particularly leukemia, to soar.

In the aftermath, there was a reckoning.

Here’s LeAnn Erickson again.

LEANN ERICKSON: Some people could justify it to themselves…that, yes, it was a terrible but necessary thing. Where others, you know, just said, couldn't be, couldn’t be us…Um, but boy, this really brought it home, the kind of devastation that was possible through the technology they were, you know, helping to develop.

KATIE HAFNER: Without human computers from the T division at Los Alamos, the atomic bomb was just an idea. Their calculations made it a reality.

CLAIRE L. EVANS: There's this connection between death and computing that is inextricable and inescapable in this history.

KATIE HAFNER: That’s Claire L. Evans again. World War II and its grim endgame marked the start of the digital age. These women and the machines they used laid the groundwork for the technology that would follow.

CLAIRE L. EVANS: It's important always to consider the fact that these women were given this opportunity because of a massive war. And it's not likely that computers as we know them today would exist if not for the needs of the second World War specifically.

KATIE HAFNER: And Johnny was a key player. His work made this technology happen. And it didn’t stop with the end of the war.

ANANYO BHATTACHARYA: He was convinced that the world would be blown up, uh, within a decade, um of the second World War.

KATIE HAFNER: That’s Ananyo Bhattacharya, again.

Johnny’s fears might also have had something to do with what happened to his family during the war.

In early 1945, just as the Germans withdrew from Hungary, Klári and Johnny received a letter from Johnny’s cousin Lili, who had stayed in Budapest. Our Hungarian translator Agi Antal found Lili’s letter by chance in a stack of documents we’d scanned. It’s the only correspondence we found that shows just how close to the bone the Holocaust was for Johnny’s family.

AGI ANTAL: One day, they had to line up and a couple of them were simply shot. Bala fell down from the third floor. I found him downstairs, laying in his blood. You can't imagine. This is not life for a human being.

KATIE HAFNER: That letter might help explain some of Johnny’s resolve to keep working on nuclear weapons.

After the war, Johnny threw himself into developing new computers that used a fraction of the time required by the punch card machines or the differential analyzer. These new computers and the algorithms they ran…

ANANYO BHATTACHARYA: …are what helped them most design a better and bigger bomb. And certainly for the hydrogen bomb, they were absolutely essential.

KATIE HAFNER: For the rest of his life, John von Neumann remained a steadfast proponent of nuclear preparedness. But his views were not always met with open arms.

KLARA VON NEUMANN: His blunt statements on this subject often shocked and turned some of his closest friends and colleagues against him.

KATIE HAFNER: As for Klári’s ethical perspective, the closest she gets to issuing an opinion is in her memoir, where she calls the atomic bomb…

KLARA VON NEUMANN: …the origin of all the suicidal problems of the world today.

KATIE HAFNER: But that’s all she says, and without any more explanation, it hangs there, and we’re left to wonder.

With the war now over, Los Alamos loosened its restrictions. And Johnny told Klári to come out west.

ANANYO BHATTACHARYA: And there's this famous telegram. And he says, bring riding and skating things if possible, opportunities very good.

KATIE HAFNER: So in 1945, over Christmas, Klári made her first trip to Los Alamos…

NIC LEWIS: …which was the worst time to visit Los Alamos ever because the pipes were freezing over and the town was without water. And despite all of the issues that the town had, she was really smitten with uh the, the kind of society there.

KATIE HAFNER: It could be that Los Alamos brought Klári back to a place she missed: her home in Budapest. Here’s George Dyson.

GEORGE DYSON: It was a strange thing about Los Alamos. For, for her, it was like, it was like back to her youth. I mean, where there were these insanely bright people. I mean, smartest people in the world. And they had a lot of parties.

NIC LEWIS: And that really captured her imagination.

KATIE HAFNER: At the end of the war, many of the women who had found computing jobs during the labor shortage ceded the work back to the men returning from overseas. Rosie the Riveter types were expected to return to the job of making dinner and raising children.

But for Klári, as the World War ended and the Cold War began, a new door opened.

When she came to the United States, she was often alone, struggling to cope with overwhelming global and personal tragedies–the unimaginable brutality of World War II and the loss of her father and her homeland. And, on top of this, Princeton, although quaint and picturesque, was by no means a paradise–and Johnny, one of her sole comforts, was often gone.

But now, after six hard years, she had reached a new land: it wasn’t a city or suburb, it was the snow-covered Wild West. At the same time, some things were so familiar. There was a frozen pond where she could ice skate, brilliant scientists who threw parties (like her family’s mulatsags), fellow Hungarians. And…

ANANYO BHATTACHARYA: Of course there is the deeply personal aspect of all of this, which is that Klári’s been separated throughout the war from her husband. And they clearly cared very deeply about each other. It was an extraordinarily tempestuous relationship, but suddenly they’re reunited and they’re working on the most powerful bomb ever developed, but at least they’re together.

KATIE HAFNER: So, after all this time, Johnny and Klári decide to team up. And the work? Turning an existing machine, and the machinery of war, into something far more powerful.

Next time on Lost Women of Science, Klári starts coding.


This has been Lost Women of Science. Thanks to everyone who made this initiative happen, including my co-executive producer Amy Scharf, producer Sophie McNulty, associate producer Ashraya Gupta, senior editor Nora Mathison, composer Elizabeth Younan, and the engineers at Studio D Podcast Production.

Thanks also to our voice actors Eva Szabo and Nandor Tary, as well as our many Hungarian translators: Agi Antal, Rick Esbenshade, Charles Hebbert, Laszlo Marcus, Alina Bessenyey Williams, and Lehel Molnar.

We’re grateful to Mike Fung, Cathie Bennett Warner, Dominique Guilford, Jeff DelViscio, Meredith White, Bob Wachter, Maria Klawe, Susan Kare, Jeannie Stivers, Linda Grais, Rabbi Michael Paley, Marina von Neumann Whitman, George Dyson, Thomas Haigh, and our interns, Hilda Gitchell, Kylie Tangonan, Leeza Kopaeva, and Giuliana Russo. Thanks also to the Computer History Museum, to Paula Goodwin, Nicole Searing and the rest of the legal team at Perkins Coie, and to the Institute for Advanced Study, the Library of Congress, and the UCSD Special Collections for helping us with our search. Many thanks to Barnard College, a leader in empowering young women to pursue their passion in STEM, for support during the Barnard Year of Science.

A special shout out to the Women’s Audio Mission in San Francisco, where this podcast was recorded.

Lost Women of Science is funded in part by the Gordon and Betty Moore Foundation, Schmidt Futures and the John Templeton Foundation, which catalyzes conversations about living purposeful and meaningful lives.

This podcast is distributed by PRX and published in partnership with Scientific American.

You can learn more about our initiative at lost women of science dot org or follow us on Twitter and Instagram. Find us @lostwomenofsci.

Thank you so much for listening. I’m Katie Hafner.

Katie Hafner

Host & Executive Producer

Katie Hafner was a longtime reporter for The New York Times, where she continues to be a frequent contributor. Katie is uniquely positioned to tell the stories of lost women of science. Not only does she bring a skilled hand to complex narratives, but she has been writing about women in STEM for nearly 30 years. She is the author of six books of non-fiction, and her first novel, The Boys, was published in July 2022 by Spiegel & Grau. Katie is also the host and executive producer of Our Mothers Ourselves, an interview podcast that celebrates extraordinary mothers.

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