Chapter Five

Throughout the Second World War, the Germans used a mechanical encoding device that they called the Enigma machine. It had been patented in 1918 or 1919 and put to use by the German army and navy by 1929. In 1931, a German working in the Cipher Office began selling information about the machine (including photographs of the instruction manuals) to the French, but neither the French nor British could break the code. It was a Pole, Marian Rejewski, who first cracked the German Enigma code in 1932 and built a replica of the machine. The Poles were then able to decode Wehrmacht radio messages until the late thirties—advances in Enigma technology foiled them as of 1937 for naval messages, and as of December 1938 for the rest of the German messages. The decoding machines Rejewski constructed were called “Bombas” (named, some said, after the ticking sounds they produced while working). The Bombas operated according to Rejewski’s insight that German intelligence operators signaled the day’s encryption key by typing in the same three letters twice in a row (for example NGHNGH) followed by the new settings for the three rotors of the Enigma machine. Knowing what these double letters signified, Rejewski then inferred the entire structure of the Enigma and its operation—the Bombas were built to sift through strings of code and find those that were likely to be messages. Through mid-1939, the Poles kept their knowledge to themselves. When the Germans introduced more rotors into the Enigma, the Poles quickly figured out how the rotors worked, but five rather than three rotors raised the number of possible combinations tenfold, outstripping the capacity of the Bombas to quickly sort through encoded messages. At the same time, the political and military situation in Poland was rapidly deteriorating, so the Poles communicated what they had discovered about the decoding of the Enigma to English and French intelligence. Rejewski and his fellow cryptographers spent the war sometimes in France, sometimes in Gibraltar, and sometimes in England, working with Allied intelligence.

Cracking the Enigma code was especially crucial for the British, since it was the code used by the German navy, and Britain was dependent on ocean traffic for every kind of supply, and therefore especially vulnerable to naval disruption or blockade. When Turing first arrived shortly after the invasion of Poland and the British declaration of war, six Bombas at Bletchley Park sifted through intercepted messages for matching letters that would reveal the settings of the German positions encoding the messages, and most of the code breaking was done by linguists, not mathematicians. The prized form of cryptanalytic intelligence was the sort that solves puzzles through a combination of linguistic sophistication and intuition. Turing was an enthusiastic puzzle solver, but since he was also a mathematician, he understood both large numbers (as in the number of combinations of letters that had to be tested in order to break a code) and probability (which combinations were likely to lead to dead ends and which were likely to be productive). It was Turing and an associate, Gordon Welchman, who were to address the problem of the extra rotors that had been added to the Enigma machine. The new “Bombes,” as they were rechristened, were designed using relays. Andrew Hodges maintains that Turing “was the right person to see what was needed, for his unusual experience with the relay multiplier [he had built at Princeton] had given him insight into the problems of embodying logical manipulations in this kind of machinery.” For his part, Welchman redesigned the wiring that constituted the instructions for the machines.

Andrew Roberts points out in The Storm of War that code breaking was not the only form of intelligence that the Allies were using even at the beginning of the war—more traditional methods such as spying, interrogating, and eavesdropping were also employed, but to break the codes meant they could listen to exchanges of information and instruction in real time, and so throughout the war, the code breakers were considered, in Churchill’s words, “the geese who laid the golden eggs” and “never cackled.”

When Turing went to Bletchley Park in September 1939, Germany seemed to have all the advantages: Stalin had signed a nonaggression pact on August 23, and the Russian army invaded Poland from the east two weeks after Germany invaded from the west. At the end of November, the Russians invaded Finland. Just after the declaration of war, the Germans had attacked an English ocean liner, the SS Athenia, killing 112 or 117 passengers (depending on the source). With the declaration of war, U-boats began steadily harassing English ships—on September 17, an aircraft carrier, the HMS Courageous, was sunk by two U-boats and went down in fifteen minutes, losing five hundred men. Historian Andrew Roberts notes that “by the end of 1939, Britain had lost 422,000 tons of shipping” by means of attacks and mines and was in danger of being isolated, without resources or even food if the German navy could manage it. The first half of 1940 was worse in every way: Finland fell, Norway fell, the first because of the passivity of the Allies, the second in spite of the Allies’ efforts. In May, the Dutch surrendered and English troops were driven back to Dunkirk, only to be evacuated, according to Roberts, because Hitler overruled the wishes of his generals, Kleist and Guderian, with a “halt order” that prevented them from pursuing and wiping out the retreating armies. France fell at the end of June, and the Battle of Britain began in July. Since the United States had declared its neutrality, the situation for Britain was desperate.

Turing’s Bombe (the first went to work in March 1940) was constructed like a large, heavy bookcase, six and a half feet high, more than seven feet long, and two and a half feet deep. The “books” were rows of motorized rotating drums, ends facing outward, twenty-six letter positions inscribed around the circumference of each. These were meant to simulate the operations of Enigma rotors. The Bombe worked as a sorter, trying out likely combinations of letters supplied by the operator to see if any German words were created as the patterns of letter correlations were changed. Most of the time, according to Turing’s mathematically based insight, sets of letters supplied by the operators (known as “cribs”) would proceed by logical substitutions to a state of self-contradiction. If the operator would suspect that A = K, for example, when it arrived at a position in which A = A, it would be self-replicating and not correct, since the decoders knew that for Enigma, a letter could not be encoded as itself. As the rotors tested the positions, they could throw out any self-replicating positions they arrived at. The greatest number of positions that had to be tested for any letter was twenty-five, the fewest, one. Each Bombe contained stacks of rotors that tested the letter combinations simultaneously. The Enigma in Germany was operated by hand, but the Bombe was motorized, so that even though Enigma encoding positions were changed every night at midnight, the Bombes (eventually there were 211) could sort through probable encoding patterns very quickly. When combinations that looked fruitful were found, the code wheels on the English replica of the Enigma machine were set to mimic what had been found, and either a message came up or it didn’t. The code breaking was painstaking and tedious work that was aided by captures of German equipment or mistakes on the part of German personnel, as well as the tendency of the German military to use set phrases and clichéd expressions. In December 1939, Turing was instrumental in deciphering five days’ worth of five rotor codes from 1938, thus demonstrating that the codes could be broken and showing how. In January 1940, Turing was dispatched to France to meet with Rejewski and his colleagues. On January 17, Turing and the Poles succeeded in breaking codes from the previous October. Throughout 1940, the code breakers made progress, aided by the capture of code wheels from a U-boat in February and another set in November. Fortunately for the British, though the Germans knew that the U-boats had been destroyed, they did not realize that the code wheels had been salvaged.

Once the Bombes had proved successful, Turing had another idea—a machine that would take the output of the Bombe and bypass the work of human decipherers by automatically translating that output from code into understandable German. It was in order to implement this idea that Tommy Flowers came to Bletchley from the General Post Office. But Flowers and Turing never succeeded in putting together that particular machine, in large part because as the war progressed, it turned out that Enigma was not British intelligence’s biggest challenge.

Konrad Zuse, now an enlisted man in the German army, was still pursuing his own interests. Early on, Kurt Pannke wrote his commander a letter, asking that Zuse be relieved of duty because the invention he was working on would be valuable to the war effort, especially the Luftwaffe. This letter succeeded only in offending Zuse’s commanding officer, who did not believe that the Luftwaffe needed any help. Zuse used the army as a place to take up chess and think about his computer theory and offered himself to work on coding and decoding, but the Germans considered that that problem had been solved by Enigma and the other machines they had devised (see chapter 6). Then Zuse’s friend, Schreyer, attempted to get authorization to work on the computer for air defense, but when he suggested that research and development might take two years, the official in charge exclaimed, “What do you mean, after we’ve already won the war!” Finally, Zuse was put to work as a structural engineer working on weapons at Special Division F, with Henschel Aircraft. The task was to develop remote-controlled bombs. One type was to be dropped from an airplane and controlled by radio until it reached its destination. Another was to be dropped into water, where it would act as a torpedo. Toward the end of the war, the division worked on defensive surface-to-air missiles.

Zuse continued to develop his computer in the evenings and on weekends, managing to bring the second version of his computer, the Z2, to the demonstration stage in 1940—though it wasn’t always reliable. Zuse reports in his autobiography that only hours before the planned demonstration took place, the Z2 could not be made to work, but then, once the audience for the demonstration had arrived, it “performed flawlessly,” only to become temperamental again once the demonstration was over. He remarks that “afterwards, I hardly ever got the Z2 to run smoothly.” The problem, he felt, was not necessarily the design, per se, but that all available relays were secondhand parts from different manufacturers that had to be reconfigured to work in the way Zuse wanted them to, and that in reworking them, he overlooked details of how they would function together. But the single flawless demonstration aroused the interest of the technical director of the Aeronautics Research Institute, which was enough to gain Zuse a contract to develop the Z3. The contract meant money, but the war effort meant that he still had to use secondhand parts.

The Z3, which was completed in 1941, did work reliably. It incorporated the following principles and design ideas:

1. Electromagnetic relay technology (not vacuum tubes)

2. Binary number system

3. Floating point (a system of locating the decimal point)

4. Word length: 22 bits

5. Storage capacity: sixty-four words

6. Control by means of eight-track punched tape

7. Input by means of specially designed keyboard

8. Output by means of display of results on a row of lights, including proper placement of the decimal point

9. High speed: 3 seconds for multiplication, division, or square root

John Gustafson, who constructed the replica of the ABC and is an expert on early computers, writes:

It was a jaw-dropping accomplishment to invent floating-point arithmetic back then and get it to work at such high speed. It wasn’t just a way of adjusting the decimal point: he could represent positive and negative infinity, undefined numbers like 0/0, and a number of other ideas that did not become standardized until the 1980s. Not many computer engineers today, given a pile of electromagnetic relays, would have the faintest idea how to build a floating-point unit out of it, especially not one that can take square roots. He was very far ahead of his time. It is also worth noting that the 64 words of memory were addressable; the computer could pick out a particular one to use by its number. The ABC didn’t have anything like that—the ABC had memory in the two drums, but the operator selected which one to use, while on the Zuse machine, it was controllable by the program tape. It was like a modern computer in almost every way except that it couldn’t do conditional branches, which is testing a number and then jumping to a different part of the program depending on whether the test was true or false.

Gustafson adds, “This is why I admire Zuse every bit as much as I admire Atanasoff … and why I’m thankful that the arrogance of the German military didn’t see the merit of Zuse’s work, since the world might be a very different place now if they had.”

Zuse continued to make do with what he could find—since he could not get hold of a tape-punching machine, he punched strips of celluloid film with a manual hole punch; since his relay coils were secondhand, they were not uniform, so he had to adjust the voltage of each one in order to get them to work together.

Even though Zuse was making progress, and he could demonstrate the usefulness of his machine for certain calculations having to do with wing flutter in airplanes, he could not prove that his computer work was valuable to the war effort. He was put back into the army again in 1941 but managed to establish that his work with Henschel was worth a deferment. His work on the computer progressed, still on his own time.

Wartime rules and regulations favored Zuse’s machine in some ways. After persuading Henschel to let him work part-time, he set up his own company to develop the computer. He writes:

Available were unskilled, mostly female workers, who had made themselves unpopular elsewhere, or who did not fit into the normal working world. So, at one time I was able to hire an excellent technical designer who had had a lengthy stay in a mental hospital. In a normal company, his eccentricities probably would have gotten on everyone’s nerves, but we didn’t have any problems with him … My book-keeper had done something very foolish when he was a young man, and he had been prosecuted for it. But he fit in perfectly with our small company … There was also the great added advantage that neither of these workers could be drafted.

One of Atanasoff’s goals in attending the meeting of the American Association for the Advancement of Science in December 1940 was to find out what other inventors were doing—he still feared that some larger, more prestigious, and better financed entity might be onto ideas similar to his. He was not giving a presentation himself, though.

One scholar, a man named John Mauchly, gave a talk about correlating weather patterns with solar phenomena such as sunspots, a subject that Atanasoff was interested in (as he was interested in allergies, soybeans, goat milk products, and home construction). In the course of his lecture, Mauchly, who was the only physics professor at Ursinus College in Collegeville, Pennsylvania, mentioned that he had devised a calculator, which he called the “Harmonic Analyzer,” to do the correlations. He detailed his design ideas and talked about his plans for building a more powerful machine. Although the Harmonic Analyzer was an analog machine, Mauchly said in his talk that he thought the future of computing was electronic, and he expected to have an electronic machine in about two years.

John Mauchly was about four years younger than Atanasoff. His background was middle-class academic, more like that of John Hasbrouck Van Vleck than like that of Stibitz, Aiken, or Atanasoff. Mauchly’s father, Sebastian, was a principal at a high school in Cincinnati, Ohio, until 1916, when John was nine and Sebastian received his PhD in physics and moved to Chevy Chase, Maryland, to become chief physicist specializing in “electricity and earth currents” at the Carnegie Institute in Washington, D.C. One thing he was interested in was the physics of lightning strikes (presaging John’s interest in weather prediction). John Mauchly was something of a prodigy and a pest, like the young Atanasoff. According to Scott McCartney in ENIAC, he had a sign over his bed that read, “What should I be doing now?” In 1919, Chevy Chase was a fairly new suburb, home to many men employed in scientific fields around the Washington, D.C., area. Twelve-year-old John, who as a five-year-old had rigged a flashlight out of a battery and a lightbulb, laid intercom wires in the trenches that workmen were digging for water lines. He was also a night owl who concocted a switch that turned off his reading light if one of his parents stepped onto the landing outside his door. In high school, he was an impressive student who planned to follow in his father’s footsteps as a physicist. By the time John was ready to go to college in 1925, though, Sebastian Mauchly had come to understand, possibly from his own experience, that there was more money in engineering than in physics, so John applied for and received a prestigious scholarship to Johns Hopkins University in engineering. But he got bored with that after about two years and transferred to the physics department, where he so impressed his professors that they decided to put him directly into the PhD program. He completed his doctorate in 1932, writing his dissertation on carbon monoxide. Here, his experience, and the conclusions he drew from it, also mirrored Atanasoff’s experience two years earlier—the calculations, which he performed on a Marchant desk calculator, proved onerous and inspired the ambition to invent a more powerful calculator.

Mauchly was just far enough behind the economic downturn when he got his PhD that he had a difficult time finding a job (Atanasoff, who found his job at Iowa State in 1930, had to take a pay cut along with all the other faculty members as the Great Depression worsened in the early thirties). Mauchly spent one year as a research assistant at Johns Hopkins and then was hired by Ursinus College, a four-year liberal arts school outside of Philadelphia founded by the German Reformed Church. At the time Mauchly taught there (and his teaching responsibilities were heavy), the college was associated with the United Church of Christ. Mauchly’s students were, for the most part, not planning to be engineers or physicists. Mauchly was the only member of the physics department—his job was to give his premed students their required course in physics and to bring returning high school teachers up to date. His salary was comparable to Atanasoff’s—$2,150. He also had a wife and two children—he had married a mathematician, Mary Walzl, in 1930.

Like Atanasoff, Mauchly engaged his students in his research interests—he put them to work correlating rainfall with the rotation of the sun, but the calculations were stupefyingly tedious and time-consuming. In 1940, while maintaining a full teaching load, Mauchly had constructed the Harmonic Analyzer.

After Mauchly’s lecture, Atanasoff hurried to the front of the room. The two scientists, both talkative and enthusiastic by nature, hit it off, and they discussed their projects for about half an hour, Mauchly describing his Harmonic Analyzer and Atanasoff describing the ABC. Mauchly showed so much enthusiasm that Atanasoff invited him to visit Ames and have a look at the machine. But Atanasoff was cautious about disclosing technical details because back in Ames, Iowa State was already beginning the patenting process, and Atanasoff was well aware that he could run into trouble if he divulged too much. Patenting was on his mind—the Atanasoffs were to meet Clifford Berry in Washington, D.C., a day or so later. After chatting with Mauchly, Atanasoff and his assistant spent four days looking through patent documents, reassuring themselves that their ideas were new and had never been patented before.

Atanasoff felt that the ABC was such a success that a significantly larger investment on the part of Iowa State was warranted and would pay off in the future. After the Christmas break, he met with college officials in order to persuade them to hire Richard Trexler, a patent attorney from Chicago with an excellent reputation. Iowa State officials balked, but Atanasoff talked them into it, and Atanasoff sent Trexler the third and last copy of his thirty-five-page description of the machine. Trexler seemed to think there would be no trouble patenting it, but Iowa State officials still did not understand the possibilities. It was only after Atanasoff received a $5,330 grant from the Research Corporation of New York at the end of March that Iowa State began to realize that the machine in the basement of the physics building might have a worthwhile, and lucrative, purpose. College president Charles E. Friley was impressed by the size of the grant—about double Atanasoff’s yearly salary and equivalent to almost $85,000 in 2010 dollars (although it was still only about 1 percent of what IBM would ultimately spend on the Aiken Mark I).

For the next six months, Friley and Atanasoff negotiated the terms of an agreement to divide up profits that might accrue to Atanasoff’s ideas. The college was stingy, to say the least—Friley wanted 90 percent of any income and, following college policy, did not want to give Clifford Berry any portion of the profits. The penalty for Atanasoff of refusing to sign would be that the college would withhold the Research Corporation of New York grant. Atanasoff, never one to be bullied, persisted until the college agreed to give him half of the profits, after expenses. From Atanasoff’s portion, Berry would receive 10 percent. The parties signed a final contract in July 1941.

There were other naysayers—Howard Aiken, having begun to work with IBM, was committed to the Mark I and not enthusiastic about the ABC. Warren Weaver, from the University of Wisconsin, who visited concerning Atanasoff’s war-related project, also reaffirmed his belief that analog was the way to go. Samuel Caldwell, of MIT, also visited the defense project, and though he was impressed by Atanasoff’s machine, he was himself working on Vannevar Bush’s Differential Analyzer (soon to be called the Bush-Caldwell Analyzer).

In the meantime, Mauchly had access to various projects that were progressing around Philadelphia and Washington, D.C. According to Scott McCartney, Mauchly took his students on one or more field trips to nearby Swarthmore College and was shown a vacuum-tube system for counting cosmic rays. What impressed him was the speed with which the vacuum tubes reacted—he observed that a vacuum tube could distinguish between two inputs only a millionth of a second apart. He saw that vacuum tubes could be much faster than switches or keys in counting, but he still had the model of a desk calculator in mind. The vacuum tubes were for input speed; he had not conceived of a binary system, in which the states of “on” and “off” would produce a logic system.

In 1939, Mauchly had seen an IBM encryption machine at the New York World’s Fair that “used vacuum tube circuits for coded messages.” Like Atanasoff, Flowers, and Schreyer, he began tinkering with various bits and pieces; he ordered tiny neon bulbs from General Electric as an experimental substitute for vacuum tubes—they were cheaper to buy and cheaper to run. But there is no evidence that he had a larger system in mind, and his only product was the Harmonic Analyzer, which may be thought of as similar to Atanasoff and Brandt’s Laplaciometer. By the time Mauchly drove to Ames, his ideas do not seem to have jelled into a systematic theory about how an electronic calculator would have worked. Although Mauchly’s biographer declares that he was a “ferocious record-keeper,” he offers no citations of records that Mauchly kept during this period, or for any date before 1943.

Faced with repeated evidence that Iowa State did not understand or particularly value himself, his assistant, or his invention, and that other well-known inventors were committed to their own ideas, Atanasoff reacted with pleasure to Mauchly’s enthusiasm. Mauchly first planned to make the eleven-hundred-mile trip west from Philadelphia in the spring but then put it off until summer. In a letter dated May 31, Atanasoff welcomed his imminent visit and suggested that he drop a line giving a date. Mauchly did drop that line, saying he would arrive either the evening of the thirteenth of June or the evening of the fourteenth, but Atanasoff failed to communicate this information to Lura, so when Mauchly arrived on the evening of the thirteenth, just as Lura was cleaning up after dinner, Lura was both surprised and put out—she had expected to get ready for the visit the next day. And to top it off, Mauchly had his six-year-old son with him. He rather impolitely asked for food and then unceremoniously handed the child over to Lura to take care of for the next four days. Lura was put on alert, and she did not like what she saw.

Atanasoff did like what he saw, though, because Mauchly was eager for information and seemed receptive to Atanasoff’s ideas—just what a man who was enthusiastic about his project and underappreciated would be looking for. In the four days that Mauchly and his son were in Ames, Mauchly, Atanasoff, and a revolving set of onlookers spent hours in the basement of the physics building. The rest of the time, especially at home, Atanasoff and Mauchly talked incessantly about the machine—how it worked, what the principles behind it were, what Atanasoff’s system consisted of. Mauchly seemed impressed—he carried the green-covered thirty-five-page description around with him and asked to borrow it and take it back to Pennsylvania. Atanasoff would not allow this, but he did allow Mauchly full access to it while he was in Ames and also allowed him to investigate the computer carefully with Clifford Berry. Sam Legvold, who was working in the next room on Atanasoff’s defense project, later remembered that Mauchly had hands-on access to the ABC and even helped Berry do a few repairs—Legvold saw him touching parts and carrying parts around.

At one point, Mauchly also asked Lura for a stack of bond paper. Lura may originally have been offended by Mauchly’s insensitivity as a houseguest, but she became alarmed by some of his other activities. Lura was a busy seamstress who often stayed up late sewing. She noticed that Mauchly was up late, too, because the light in his room was on, and she suspected that he was writing. She feared that he was not only taking an interest in the ABC but planning and working to steal her husband’s ideas. While Mauchly was in Ames, she warned Atanasoff not to talk as freely and in such detail as she witnessed him doing, and Atanasoff acknowledged her caution. But he did allow Mauchly free access to the computer, and he did answer his questions. He later said that his impression at the time was that Mauchly had neither the background nor the knowledge that would make him capable of stealing the ideas, or understanding them well enough to be able to reproduce the ABC back in Philadelphia. For Atanasoff, the temptation to show off his invention was too great, certainly in part because even while the president of Iowa State was attempting to secure the future profits of the ABC, Atanasoff’s colleagues there were almost universally either skeptical about or indifferent to what he was doing.

Subsequent controversy about whether Mauchly or Atanasoff should be given credit for the invention of the computer (or, to be precise, the invention of the calculating device that led to the invention of the computer) has revolved around the question of whether the ABC was operational at the time Mauchly visited Ames. Those who give the credit to Mauchly say that it was not. Those who give the credit to Atanasoff say that it was. But one thing that John Gustafson and his fellow reconstructors discovered when they built the replica and delved into the history of the ABC was that Atanasoff’s friend in the statistics department, Professor George W. Snedecor, “would send problems over to Atanasoff and the ABC would solve them. Then the secretary, Clara Smith, would check the results on a desktop calculator. And they would be correct.” The ABC was functional.

In the summer of 1941, Mauchly entered a course at the Moore School of Electrical Engineering at the University of Pennsylvania, a much more prestigious and well-connected institution than Ursinus College. The course was given at the behest of the Department of War and was designed as a cram course in electronics for young scientists in other fields. Mauchly, thirty-six, was hoping that he would learn some things that would move his weather project forward. It was there that he met his partner-to-be, J. Presper Eckert, age twenty-two, just graduated from the Moore School in engineering. Like Atanasoff, Berry, and Mauchly, Eckert had a long history of high-energy fiddling, but unlike the others, he was a child of privilege. His father was a Philadelphia developer who hobnobbed with such celebrities as Ty Cobb and Douglas Fairbanks, Jr. Young Eckert went to school—the William Penn Charter School—in a chauffeur-driven limousine. Father and son were both well traveled—Pres, as he was known, had already visited the Pyramids, among other exotic locales. At an amusement park in Paris, he got the idea for a project that won the Philadelphia Science Fair when he was twelve—a four-by-six-foot pond-like tub with magnets resting in the bottom. He steered a model sailboat across the surface of the water using a steering wheel connected to the magnets. He built radios and music systems and installed them around Philadelphia, including a system for a cemetery that, according to Scott McCartney, “masked the unnerving sound of gas burners in the nearby crematorium.” His connections around Philadelphia gave him access to such innovative communications companies as Philco, RCA Victor, and others. He was a member of the Engineer’s Club of Philadelphia and spent time with Philo T. Farnsworth, an inventor of the television who settled in Philadelphia in 1931.

In 1937, according to Scott McCartney in ENIAC, Pres Eckert scored second in the nation on his math SAT and was accepted to MIT, but his mother and father prevailed on him to stay home and go to the Wharton School. Within a few months, he transferred from Wharton to the Moore School, to study engineering. But he was not a good student—he did only what he wanted to do and occasionally fell asleep in class. According to McCartney, upon being awakened by the dean of the Moore School and asked, “If you’re going to come to class, why can’t you stay awake?” Eckert responded, “Why?” Every day, he wore a clean, pressed, monogrammed white linen shirt to class. After he graduated in the spring of 1941, Eckert joined the same ten-week cram course as Mauchly, and the two were assigned to be lab partners. Mauchly was the oldest student in the class, and one of two PhDs. Eckert was the youngest. At the end of the summer, Mauchly was hired away from Ursinus by the Moore School to teach physics, a replacement for other faculty who were leaving to join the war effort. According to McCartney, Mauchly’s hiring was not a sign that the University of Pennsylvania was impressed by him or considered him promising, only that he was the only available candidate.

The other PhD in the course was Arthur W. Burks, originally from Duluth, Minnesota, whose PhD, from the University of Michigan, was in philosophy (though his BA was in physics and mathematics). He had completed his dissertation, “The Logical Foundations of the Philosophy of Charles Sanders Peirce,” on a brilliant but troubled and even tragic contemporary of William James whose work is much better appreciated today (in part thanks to Burks) than it was during his own lifetime. In the summer of 1941, Burks was twenty-five. He was hired to teach at the Moore School that fall, like Mauchly. He eventually joined the ENIAC team (ENIAC stood for “Electronic Numerical Integrator and Computer”—Mauchly added “and Computer” after visiting Ames), and, like Mauchly, found a wife, Alice, among the women mathematicians who were computing firing tables. Alice had gotten her BA from Penn in 1944 in mathematics.

The teaching load at the University of Pennsylvania was lighter than that at Ursinus and left Mauchly time that he planned to use improving his Harmonic Analyzer. In October, he wrote Atanasoff, specifically asking, “Is there any objection, from your point of view, to my building some sort of computer which incorporates some of the features of your machine? For the time being, of course, I shall be lucky to find time and material to do more than make exploratory tests of some of my ideas, with the hope of getting something very speedy, not too costly, etc.” Mauchly was also looking toward the future—he asked in the same letter whether “in the event that your present design were to hold the field against all challengers, and I got the Moore School interested in having something of the sort, would the way be open for us to build an ‘Atanasoff Calculator’ … here?” And he reported that Irven Travis, the man who had designed an analog “analyzer” on the model of the Bush-Caldwell Analyzer at the Moore School had entered the navy and departed. Mauchly was quite familiar with Travis’s machine and had discussed it in depth with Travis. Travis later reported that he had discussed his variation on the Bush-Caldwell Analyzer with Pres Eckert when Eckert was his student. Before leaving for the navy, Travis had already considered the idea of building a computer on the scale of Aiken’s at Harvard—he had done a study for General Electric that estimated the cost at about half a million dollars. GE did not want to spend that kind of money, but Travis did give Mauchly a bibliography of material about it. Atanasoff responded cautiously, more cautiously than he had acted in June. He wrote, “Our attorney has emphasized the need of being careful about the dissemination of information about our device until a patent application is filed. This should not require too long, and of course I have no qualms about having informed you about our device, but it does require that we refrain from making public any details for the time being.” He went on to say that with these considerations in mind, he had refused an invitation to describe the machine at the meeting of the American Statistical Association.

By the summer and fall of 1941, Turing’s work on the Bombe and the Enigma code (which the British referred to as “Ultra”) had profoundly impressed his colleagues at Bletchley Park, and he had also impressed Winston Churchill. The code breakers had been successful: so many German supply ships were sunk in the late spring that the British authorities worried that they had handed the Germans irrefutable evidence that the cipher was broken. As Konrad Zuse had seen, though, the Germans simply decided that such a thing was impossible and continued using Enigma. After May, the work at Bletchley Park met with a few small obstacles, but by the autumn of 1941, the British were confident that they could decode any German naval communication, and if the British navy used their knowledge wisely, they could severely limit the vulnerability of British forces to German naval operations.

There was, however, another more complex encoding system that the Germans were working with, which the English decoders at Bletchley Park called “Tunny.” When Alan Turing grew famous in the 1980s, almost all of the information concerning the importance of Tunny and its solution at Bletchley Park was still secret. These secrets were finally revealed in 2006 with the publication of Colossus by B. Jack Copeland and colleagues. While Enigma was used by the German navy, Tunny was used by the German High Command, including Adolf Hitler. After June 1941, Tunny was produced by a more complex encoding machine, the Lorenz Schlüsselzusatz (“Extra Keys”). The security surrounding the breaking of the Tunny codes at Bletchley Park would shape computer history but would remain top secret until the 1990s, long after the death of Alan Turing and long after most historians and students had come to what turns out to be a misunderstanding of the progress of World War II.

Certain details and images of Turing at Bletchley Park have remained a part of the cultural image of him—as recently as September 2009, in discussing the possibility for posthumous honors for Turing, Geoffrey Wansell referred in the Daily Mail to some of his well-known habits: “Notorious for his idiosyncrasies—he would tie his tea mug to the radiator so that no one else could use it, and ride his bicycle wearing a gas mask simply to avoid hay fever—Turing was, nevertheless, keen to ‘fit in’ … Despite his high-pitched voice and increasingly odd behaviour—he would sometimes run the 40 miles from Bletchley to London to attend meetings.” Wansell points out, “Turing was critical to the war effort.” In his spare time at Bletchley Park, Turing, like Zuse, was also thinking about chess, partly because the workforce at Bletchley played a lot of chess in off hours. As a result, Turing’s imagination, which seems always to have had a philosophical bent, turned to another thought machine—one that would use probable outcomes to extrapolate the relative benefits of various chess moves. The idea was to create a machine that could simulate human decision making. He also thought about mathematical problems, saying, “Before the war, my work was in logic and my hobby was cryptanalysis, and now it is the other way round.” In October 1941, right about the time that Mauchly was feeling out Atanasoff about whether he could use some of his ideas, Turing and a few of his colleagues were writing to Winston Churchill to request additional typists and other staff. In 1941, the war was going better than it had in 1940, partly because Hitler broke with Stalin and attacked the Soviet Union in late June of that year, giving himself only about three months to take the major Russian cities before the onset of winter—according to historian Andrew Roberts, if he had attacked two months earlier, as originally planned, he might have had a chance of prevailing. Germany did manage to take Kiev, Minsk, Kharkov, and Rostov, though just before Pearl Harbor they had to call off the attack on Moscow. The Allies were making progress in Africa, too, but at Bletchley Park, those working on the Enigma cipher were wondering about the Americans. They were certain that Roosevelt would enter the war fairly soon and were nervous about whether the secrets of their methods could be entrusted to the American navy. As it turned out, the Germans declared war against the United States on December 11, 1941. According to Turing’s biographer Andrew Hodges, when British intelligence then attempted to share information derived from the operations at Bletchley Park about German U-boat locations in the Atlantic with the U.S. Navy—in particular, “the operation of fifteen U-boats off the American coast at the declaration of war”—the navy ignored the information, resulting in huge losses in the Atlantic at the same time the United States was deploying many vessels to the Pacific. The war in the Atlantic, which had been going well, suffered serious setbacks.

In Ames, the entry of the United States into World War II brought work on the ABC, particularly the electric spark card-marking mechanism, to a halt. Though Atanasoff and Berry felt that if they could find the right card stock, they could make the charring mechanism work, the start of the war in America made supplies and parts of all kinds scarce, and Atanasoff had to turn his full attention to his defense project. Berry had to turn his full attention to looking for a job in the defense industry—he was due to receive his master’s degree in May. In their spare time, both men assembled and polished the information needed for the ABC patent application, which, Iowa State continued to assure Atanasoff, would be filed any day. In the summer of 1942, Berry married Atanasoff’s secretary and departed to take a job in California. In September, Atanasoff himself left Iowa State for a job at the Naval Ordnance Laboratory in Washington, D.C., though he retained his full professor position at Iowa State with the plan of returning after the war. He had done well in Ames—his salary was $5,800 a year, more than twice his starting salary in 1930, which meant that his salary for defense projects would also be a high one. And he was convinced that between them, the patent attorney in Chicago and the administrators at Iowa State had the patenting of the ABC well in hand. The machine itself he left in the basement of the physics building.

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