“Had we been called upon by the Staff to do so,” Hope wrote, referring to Oliver, “we could have furnished valuable information as to movements of submarines, minefields, minesweeping etc. But the Staff was obsessed with the idea of secrecy; they realized that they held a trump card and they worked on the principle that every effort must be made to keep our knowledge to ourselves, so as to be able to keep it up our sleeves for a really great occasion such as the German Fleet coming out in all their strength to throw down the gage in battle. In other words the Staff determined to make use of our information defensively and not offensively.” Commander Hope applied the underlines.
IT WAS tedious work. Hundreds of intercepted messages came chattering into the building’s basement every day, where they were placed in dumbbell-shaped canisters, which in turn were shoved into vacuum tubes and, with a satisfying fwump, launched up through the building. Upon reaching Room 40, the containers tumbled into a metal tray with a clatter that “shook the nerve of any unwitting visitor,” according to one of the group’s code breakers. The noise of these arriving messages was especially hard on the men assigned to the night watch, who took turns sleeping in a bedroom that connected two larger offices. They endured an additional hardship: mice. The rodents infested the bedroom and late at night trotted over the faces of the sleeping men.
“Tubists” took the messages from the vacuum canisters and passed them on to the code breakers. The tubists were officers who had been injured badly enough in the war that they could no longer fight. This cadre included a one-legged man named Haggard and a one-eyed British officer named Edward Molyneux, who would go on to become an acclaimed designer of clothing in Paris.
The most tedious part of the job was writing the complete text of each message into a daily log. Churchill insisted that every intercept be recorded, no matter how routine. As the number of intercepts multiplied, this task became “soul destroying,” according to one Room 40 member; the log “became an object of hatred.” But Churchill paid close attention. In March 1915, for example, he scrawled on one of Hope’s decrypts, “Watch this carefully.”
The group learned over time that even a seemingly innocuous change in the character of routine messages could signal an important new action by the German navy. Wrote Commander Hope, “Any messages which were not according to routine, were to be looked on with great suspicion, and in this way we were able to build up a large number of signs and portents.” The British wireless operators who listened in on German communications came to know just by the sound of a transmission whether it came from a submarine. They found that U-boats first took a few moments to tune their systems and then began each transmission with a kind of electrical throat-clearing, five Morse signals: dash dash dot dash dash. “The final note,” Commander Hope said, “is high-pitched … and has a wailing or whining character when sending.”
Thanks to captured charts, Room 40 also knew that the German navy had divided the seas around England into a grid to better direct the travels of surface ships and submarines. The North Sea had been broken into squares six miles on a side, with each square assigned a number, according to Hope. “Whenever any of their vessels was at sea, she was continually signaling her position by saying what square she was in.” By plotting these on a chart, Hope wrote, Room 40 learned which routes German ships and U-boats followed. Some squares were consistently empty: “It was only reasonable to suppose that these blank spaces were mined areas.”
Over time, thanks to Room 40’s intercepts and information gleaned from interrogations of captured submariners, both Room 40 and Capt. Blinker Hall’s intelligence division developed a sense of the flesh-and-blood men who commanded Germany’s U-boats. A few, like Kapit?nleutnant Weddigen, the man who sank the cruisers Aboukir, Cressy, and Hogue, were daring and pushed their crews to the limit. A captain of this kind was called a Draufganger, or dashing commander. Another commander, Claus Rücker, was said to be “a bully and a coward.” In contrast, Walther Schwieger was described in several intelligence reports as a good-natured soul who was well liked by his crew and peers, “a very popular and pleasant officer,” as one report put it.