MacArthur’s goal was to retake the Philippines and invade Japan. Operation Cartwheel called for the U.S. Army and Navy to work together in this region. As MacArthur’s troops made beach landings and fought a fierce, dug-in island adversary, Admiral William “Bull” Halsey would support them from ships in the South Pacific. The U.S. Army at this juncture had more troops fighting in the Pacific than it did in the Atlantic war theater. Those soldiers faced months, maybe years, of beach and jungle warfare. They needed intelligence to tell them where the enemy’s land troops were and what they were getting into. Even with JN-25 being read, the United States needed access to Japanese Army communications.
For a code breaker, no situation is more stressful than knowing lives depend on your own success or failure. If you crack the code, people will live. If you don’t, they may die. Once more a unit was set up to break the Japanese Army systems, led by Frank Lewis, one of Friedman’s most brilliant—if unlikely—hires. Lewis, the Utah-bred son of an Englishman turned cowboy, was a gifted musician, a lover of puns, and a puzzle enthusiast who would later write the cryptic crossword for The Nation. Before the war, he had been languishing, bored out of his mind, as a secretary in the death benefits section of the civil service. Friedman snatched him up. Friedman’s top women also worked the Japanese Army problem; after the move to Arlington Hall, all found themselves sweating it out on the hot upper floors of the old schoolhouse. The rooms had a country club flavor that would have been lovely and relaxing, had they not been so crowded and had the task not been so daunting. It was not unusual to find an exhausted code breaker napping in a tub.
Matching wits against an unseen enemy, their little band was vastly outnumbered.
“Visualize, if you will, the entire communications set-up of the Japanese military forces, with many thousands of men whose entire existence centered around the preparation and transmission of messages,” Lewis later wrote, “and then contrast that huge organization with the small group of technicians at our own establishment.”
Much of their challenge had to do with the island environment in which the foe was operating. As the Japanese Army spread out around the Pacific, its cryptographers had to create new code systems and subdivide old ones. The Japanese devised a host of minor codes and at least four major four-digit systems: one for ground forces, another for air forces, another for high-level administrators, and another for the “water transport organization,” which was a vital lifeline of marus, or commercial merchant ships, commandeered by the military to carry resources, including oil, food, and equipment. Each system was identified by a discriminant—an unenciphered four-digit code group at the beginning. It was a huge tangle, and as of January 1943 there were just fifteen American civilians, twenty-three officers, and twenty-eight enlisted men working on breaking all of them.
One of the civilians was Ann Caracristi, the twenty-three-year-old who washed her hair with laundry soap. She had been recruited out of Russell Sage, a women’s college in Troy, New York. Ann had grown up in Bronxville, in a middle-class family of Italian-Austrian heritage. She had two older brothers, one of whom was serving in India. Her father, a businessman and inventor, had permitted the older brother to attend college, but the younger wanted to be a liberal arts major and that was not considered sufficiently serious-minded, so he could not go. Her father died while Ann was in her teens, and Ann herself was able to attend college thanks to a friend of her mother, who saw her intellectual promise and helped persuade a group of Bronxville women to finance her tuition. She played basketball and edited both the campus newspaper and the literary magazine. She did not see herself as smart, but those who instructed her saw differently.
In May 1942, the Army Signal Corps had met with emissaries from twenty colleges gathered at the Mayflower Hotel, including Dr. Bernice Smith from Russell Sage. The Signal Corps asked Dr. Smith to handpick a few of her top students. As a result of these faraway high-level meetings, Ann Caracristi found herself sitting in the office of a Russell Sage dean she knew well. The dean told Ann and two classmates that there were jobs in Washington for women with brains and imagination. Thinking it a bit of a lark, the three friends traveled down after graduation, taking rooms in a Wyoming Avenue boardinghouse that had once housed the Armenian embassy. Soon enough, Ann too found herself laboring under the eaves in the attic of the Arlington Hall school building. She started by learning to edit traffic, sorting intercepts to be typed up and put onto IBM punch cards so that code groups could be compared. Everybody was playing it by ear, and newcomers could—and did—innovate techniques. Another female newcomer suggested they first edit by date and time, as a way to identify duplicate messages. The suggestion—it came to be known as de-duping—revolutionized the process.
Progress was slow, however, even with the influx of helpers. To the naked eye, the major Japanese Army code systems consisted of an unbroken string of four-digit numbers: 5678 8757 0960 0221 2469 2808 4877 5581 1646 8464 8634 7769 3292 4536 0684 7188 2805 8919 3733 9344, say. The code breakers knew only that the systems were enciphered codes, somewhat like JN-25, involving both a code and an additive book. But the Arlington Hall team could not figure out the encipherment method; despite attack after attack, they were stuck.
At the suggestion of a visiting Bletchley Park colleague, the brilliant John Tiltman, they decided to break the job down to see if they could manage to crack even just the address that began every message. This was a series of only a half dozen or so code groups, but they were important ones. After a Japanese Army message was enciphered, it passed to a radioman who attached an address specifying who the message was from (the hatsu), whom it was going to (the chiya), and where those people and their units were located (the ate, or address). The address designated the army command, installation, or officer for whom the message was intended.