This post is the conclusion of the preceding one, which please read first.
When I was a student at the School of Oriental and African Studies (SOAS) in London in the late 1940s, my best friend was a linguist named Peter Judd. He was a Natural Bilingual: mother French, father English. But his mother had died while he was very young and he'd been educated in England. So his English was dominant and he'd also learnt the usual grammar school languages: French and Latin, and perhaps Greek or German. By the time I met him, he was doing a PhD in phonetics under the influential linguist J R Firth. But during WWII he was called up for service in the Royal Navy. However, to his surprise, the Navy didn't send him to sea; instead it sent him on a crash course to learn Japanese. He never told me what he did with his Japanese. In the 1940s and for long afterwards it was still secret. Now, at BP, I began to understand.
"After Pearl Harbor… the need for Japanese linguists for military and intelligence work became acute… The War Office [which had previously refused funding for Japanese courses] clamoured for Japanese speakers and SOAS set up a special course for grammar school boys in their last year at school… But SOAS was bombed and the course did not start until May 1942... They also ran a 10-week course in Japanese radio signals."I used to think that all the work on breaking the Japanese codes had been done by the Americans. While the Germans were developing Enigma, the Japanese had been developing their own machine for their diplomatic codes. The US Army code-named it Purple. The Americans broke into its code by 1940, and the intelligence obtained from it, which they called Magic, became the equivalent of the British Ultra. However, the Japanese used many more totally different codes and ciphers than the Germans during the course of the war, probably 55 in all. The most important of them operationally was their naval code JN25. It was decrypts of JN25 that enabled the Americans to prepare for the Battle of Midway and to shoot down Admiral Yamamoto's plane over the Solomon Islands – this last exploit a terrible blow to Japanese morale.
But the British too worked on JN25, and Hut 7 at BP also had a section that worked on Japanese Army Air Force Codes. The British had their own reasons. Large pieces of what was then still the British Empire lay in the Pacific theatre of war. Thus it was JN25 decrypts that gave them warning of a Japanese attack on the British fleet at Colombo, which was intended to be another Pearl Harbor.
"HMS Anderson was the Intelligence Unit of the Eastern Fleet's Headquarters at Colombo, linked to Bletchley Park. They were working one sultry afternoon in Colombo on a message that described plans for a massive attack somewhere. Then they spelt out the name of the place that was to be clobbered – KO-RO-N-BO. An electric shock ran through the up-to-then relaxed office."Admiral Somerville moved his fleet out of Colombo in time.
The intercept stations
Most of the enemy communications traffic was transmitted by shortwave radio. That was the Achilles heel that made it possible to intercept it. But shortwave has serious limitations, not only in its geographical range but also because its quality varies according to the time of day. To maintain constant surveillance, many radio monitoring posts were needed and some of them had to be moved around as the Japanese advanced. Thus, as we have just seen in the Colombo example, BP was more than BP itself. It was the coordinating centre of a far-flung web of outstations and listening posts. There was more to BP than meets the visitor's eye.
Having absorbed as much as we could of BP in one day, we pilgrims retired to a good meal at the Three Trees in Milton Keynes. It's typical of a current trend in England: an old pub turned comfortable restaurant. Seventy years on and no reminder of the astute heroism we had been witnessing down the road. To sum up, if you're in London with a day to spare and you're interested in the history of cryptology, computers, translation or WW2, don't miss Bletchley Park.
Sue Jarvis. Japanese Codes. New Edition. Report 6. National Codes Centre, Bletchley Park Trust, 2009.
Hugh Denham. Codebreakers. Edited by F. H. Hinsley and A. Stripp. Oxford University Press, 1993.
Michael Smith. The Emperor's Codes: Bletchley Park's Role In Breaking Japan's Secret Cyphers. Penguin, 2010.
Flowerdown, Hampshire, UK listening station. It was linked to BP and was bombed twice in one week.