Beating Nazi Germany's Enigma Code Won The Allies World War II

November 15, 2019 Topic: History Region: Europe Blog Brand: The Buzz Tags: IntelligenceWorld War IIEnigmaNazi GermanyAllies

Beating Nazi Germany's Enigma Code Won The Allies World War II

Cooperation between America and Britain was crucial.

When the Kriegsmarine switched to these updated ciphers and encryption machines in February 1942, Bletchley Park’s analysts knew they had been locked out of Enigma at a most inopportune time. Admiral Dönitz’s marauders were already killing hundreds of men and destroying tons of badly needed war matériel off the shores of North America. Raw United States naval and air forces could not combat this growing menace on their own. The British had vast experience in antisubmarine warfare, as well as the super-secret Ultra program, but how much were they willing to share with the Yanks?

Neither nation wanted to cooperate at first. “The World War II relationship between the British and American cryptanalysts began in confusion and mistrust,” observed historian Colin Burke. “The combination of British reluctance, America’s divided armed services, misunderstood agreements, and lost messages almost led to an end to the joint intelligence program.”

The U.S. Army and Navy maintained separate information gathering organizations, an arrangement that led to much wasted time and duplication of effort. Prior to Pearl Harbor, American codebreaking efforts focused on Japanese activity to the near exclusion of Germany. This was especially true of the U.S. Navy, whose communications intelligence division, OP-20-G, assigned a mere five analysts to work Enigma throughout most of 1941.

Although Prime Minister Winston Churchill and President Franklin D. Roosevelt pledged full cryptologic cooperation in mid-1940, the first U.S. visit to GC&CS took place almost nine months later. During February and March 1941, four American military intelligence officers toured the codebreaking facilities there. They came bearing gifts: copies of the “Purple” machine that decrypted Japanese diplomatic ciphers, as well as valuable data on Japan’s military codes. 

In return, the Americans were shown a Bombe and given technical drawings of Germany’s Enigma. Bletchley Park also promised a Bombe would be sent on to the States as soon as one became available. This device was never provided; OP-20-G received blueprints in mid-1942 only after lodging a series of formal protests.

The American team chafed under their hosts’ security requirements, which included frequent warnings not to write down or discuss what they had seen with anyone not previously approved by GC&CS. And they were not allowed to see any operational data—kept hidden was such information as how Bletchley Park deciphered U-boat locations.

In fact, it was with extreme reluctance that Brigadier Stuart Menzies, head of British Intelligence, allowed the U.S. any access to Ultra’s secrets. He knew that if one word leaked, his opposite numbers in Germany would immediately change their ciphers and close the door on GC&CS’s invaluable cryptanalytic activities. Menzies also recognized that the United States, then a neutral power, was notoriously poor at keeping secrets, suggesting to Churchill in June 1941 that “the Americans are not in any sense as security minded as one would wish.”

Great Britain viewed the process of information sharing as a “need-to-know” matter. To preserve Ultra’s integrity, all decryption activities were to be performed in England and material deemed useful to U.S. forces sent by encrypted cable across the Atlantic. In no way did London want the Yanks to build their own Bombe. The risk of German agents finding out about it was just too great.

Yet, as horrified Americans watched torpedoed oil tankers burn just off their coastline, a rising clamor to stop the U-boats reached influential ears. In Washington, Chief of Naval Operations Admiral Ernest J. King demanded immediate action. His orders to the cryptanalysts of OP-20-G were both simple and direct: do whatever it takes to pierce these formidable new ciphers.

Navy researchers and scientists from the Massachusetts Institute of Technology (MIT) promptly set out to design an all-electric decryption device capable of defeating the four-rotor Enigma. This was done against London’s wishes, but as the bloody spring of 1942 dragged on into summer GC&CS admitted it could make little progress against the Kriegsmarine’s new enciphering systems. Without a functional alternative of their own to offer, British intelligence chiefs had no choice but to let the United States move forward on a solution.

The theoreticians at MIT enjoyed a favorable working relationship with American industry, most notably the National Cash Register Company (NCR) of Dayton, Ohio. It was in Dayton that the Naval Computing Machine Laboratory (NCML) was established in March 1942. NCML took over NCR’s former night school, Building 26, where civilian and military workers set out to construct a U.S. Bombe.

Selected to lead this development team was NCR’s chief of electrical engineering, Joseph R. Desch. At age 34, Joe Desch had already distinguished himself by inventing miniature fast-counting vacuum tubes called thyratrons that would later form the basis for modern computer technology. Desch’s pedigree as a second-generation German-American, however, aroused considerable suspicion. He could not visit his German-born mother without permission and was constantly shadowed by plainclothes naval agents throughout the war.

So concerned was the Navy over Joseph Desch’s loyalty that it assigned him a “liaison officer” named Lt. Cmdr. Ralph I. Meader, who as an added security measure slept in the Desch family’s spare bedroom. Meader also administered the NCML’s rapidly expanding activities in Dayton, working with OP-20-G to ensure the uninterrupted flow of personnel, materials, and funding. Part of his job involved pressuring Building 26’s workforce to increase productivity. “Men are dying,” Meader would say, “and you’re responsible for their deaths if you don’t get the job done.”

There were many early setbacks. MIT’s all-electric concepts were soon deemed impractical, as they required computing capabilities that did not yet exist. Desch next drew up plans for an electromechanical Bombe, one inspired by Turing and Welchman’s version but that incorporated several improvements. In practice, a production American Bombe ran from two to six times faster than its British counterpart.

The project benefitted from a gradual warming of relations between OP-20-G and GC&SC starting in the summer of 1942. Alan Turing visited Dayton that December, noting with interest the Americans’ thyratron memory tubes but also expressing concerns over other aspects of their prototype. Joe Desch ignored Turing’s criticism of his automatic rewind feature but eventually followed the British mathematician’s recommendation to standardize on one size of commutator wheel.

This wheel, which replicated Enigma’s rotor, was easily the most labor intensive element of Desch’s design. One commutator required 104 precisely hand-wired contacts, and each Bombe ran 64 commutators. To meet initial production requirements, roughly 6,000 of these wheels had to be manufactured quickly, accurately, and by people who could keep their mouths shut.

In April 1943, the first of 600 smartly uniformed U.S. Navy WAVES (Women Accepted for Volunteer Emergency Service) began arriving in Dayton to assemble cryptanalytic Bombes. Together with 200 male sailors they toiled in shifts around the clock, soldering colored wires to commutators. For security’s sake, the WAVES never saw both sides of a wheel; nor were they allowed to enter any area other than their assigned workspace.

The activity in Building 26 had to be kept highly classified. “We were sworn to secrecy,” said former WAVE Adeline Sullivan, “and periodically reminded about the Espionage Act.” Another WAVE, Veronica Mackey, vividly recalled a Navy officer telling her, “If you talk about what goes on here, you’ll be shot.” Mackey was stunned by the man’s blunt warning. “He got our attention,” she later remarked.

At the beginning of every shift, hundreds of WAVES marched one mile from their quarters in Sugar Camp—a former NCR sales training facility—to Building 26. After presenting proper identification to shotgun-armed Marine guards, the women entered large rooms where, according to Ronnie Mackey, “They gave you a soldering iron and we would … wire those little wheels. And when you’d finish one they promptly brought you another one.”

None of the Dayton WAVES realized how much Joe Desch and the Navy relied on their attention to detail. Early test machines spun commutators around at a rate of nearly 1,800 revolutions per minute. The slightest imperfection might send wheels flying across the room and set progress back days or weeks. And there was always pressure from Washington and Lt. Cmdr. Meader: every day you waste, more men die.

Throughout the spring of 1943, Desch’s team struggled to produce a functional apparatus. Their two prototypes, nicknamed Adam and Eve, continually leaked oil from gearboxes and other moving parts. Each Bombe housed 10 miles of wire and more than a million soldered connections, a mechanical nightmare for those repairmen whose job it was to keep these temperamental devices operational.

The Americans kept at it. Shortly after noon on May 28, two Navy technicians, Machinists Mate First Class Phil Bochicchio and Radioman K.P. Cook, fed a “menu” of intercepted Enigma settings into Adam and started up their Bombe. The contraption whirred noisily for a while before abruptly shutting down in what appeared to be another malfunction. The sailors gaped in amazement when Adam suddenly clattered back to life, rewinding itself onto a suspected commutator position just as designed. They ran the same data through Eve, which produced an identical set of wheel settings.

Bochicchio and Cook presented their findings to Lt. Cmdr. Meader, who transmitted this information via secure line to OP-20-G in Washington. Analysts there ran the decrypted settings through a checking device, then announced, “Jackpot.” The four-rotor Enigma had been defeated.