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The very short intervals to be measured were displayed on a CRT (Cathode Ray Tube, the forerunner of the TV picture tube). A beam of electrons was rapidly swung back and forth, impinging on a phosphor screen which glowed when electrons struck the phosphor. The returning pulses moved the electron beam up, painting a "blip" on the screen. The time between blips represented distance to the target; in fact the display screen was calibrated in miles. Various improvements were made so range, height and bearing could be measured.
They had observed British coastal installations sporting some rather odd-looking antennas, none of which were bowl-shaped, and decided they couldn't possibly be connected with radar. Besides, they were difficult to attack. This was to be their downfall in the Battle of Britain.
Knowing German plans from Enigma intercepts and radar information, the British were able to keep their fighters on the ground until the bombers showed up. German pilots couldn't understand how the British seemed to know exactly where they were going to be and when.
Wing Commander Leigh of the Coastal Command proposed placing a powerful movable searchlight in the nose of the plane to illuminate the submarine at night. After the usual considerable battles with officialdom, the Leigh light was adopted. The surfaced sub was acquired on radar, and when contact was lost at about a mile the light was switched on. The effect on a submarine crew was considerable - cruising along with no warning, a blinding 22 million candlepower light, and depth charges.
As with any new weapon, it is only effective until a countermeasure is developed. The Germans soon equipped their subs with "Metox" receivers, which picked up the radar pulses, and gave plenty of warning to dive to safety.
Prime Minister Winston Churchill realized that England's only salvation was to involve the United States in the conflict. Franklin D. Roosevelt, President of the United States, was sympathetic to the British cause, but his hands were tied by the complexities of American politics. It was a delicate situation - how could America supply vital war materiel to Great Britain and, at the same time, maintain its neutrality?
The Irish Free State (Republic of Ireland, or Eire) had been established in 1921, leaving Northern Ireland still closely tied to Great Britain. As part of the settlement, some naval bases in the Irish Republic were occupied by the British. At the start of World War II, the Irish Republic flatly refused to become involved unless the whole island was united under their rule. The British declined, and relinquished their bases. However, they still maintained facilities in Northern Ireland, which guarded the vital Atlantic approaches. (The Republic of Ireland managed to stay neutral throughout World War II.)
Roosevelt wanted the freedom to selectively supply arms to other countries, but Congress insisted on a mandatory embargo to all countries.
As British supplies of U.S. dollars and gold reserves were rapidly depleted, technology was traded for credit. The magnetron, an essential radar component, had been invented by the British, but was traded to the U.S. for arms.
Nov. 5, 1940, Roosevelt was elected to a third term, the first ever for a U.S. President, his hands now free to send vitally needed aid to Great Britain. On Jan. 10, 1941, the "Lend Lease" program was instituted. By War's end 30 billion dollars had been lent to Great Britain.
In World War I, the Japanese were aligned with the Allies. At an arms limitation conference between the major powers at the conclusion of World War I, they wanted parity with Great Britain and the United States. However, decoded messages showed they would settle for a ratio of 1:1:6. Knowing their bottom line, the other powers insisted on this reduction, which was to have great repercussions for Japanese naval strength at the start of World War II.
In 1928 a commercial Enigma was, through great foresight, purchased and shipped to America before it was withdrawn from the market. On May 1929 Henry Stimson, the new Secretary of State, naively stated "gentlemen do not read each other's mail" and closed "The Black Chamber" (a generic term for cryptanalysis operations), which was headed by Herbert Yardley. With his command disbanded, a disaffected Yardley wrote The American Black Chamber in 1931. The book is an exposition, in detail, of the cryptanalytical techniques used to break foreign codes. Ostensibly, Yardley wrote the exposé because there was no reason to keep the techniques secret. The book caused quite a sensation in its day!
Fortunately, its functions were transferred to the Signal Intelligence Service under the brilliant direction of William Friedman, and codebreaking efforts continued as if nothing had happened. Born Wolfe Friedman in Russia, his first name was changed to William when his family emigrated to the United States in 1892. He was appointed Chief Cyptanalyst of the Signal Corps in 1922. Predictably, Friedman's efforts were primarily concerned with Japanese traffic. Although Friedman is generally credited for breaking the Japanese codes, his subordinate, Frank Rowlett, was mainly responsible for the effort.
Oddly enough, the Germans had actually demonstrated their Enigma to Major P. W. Evans of the U. S. Army Signal Corps in October, 1930. They also showed him a large 10-rotor machine and an even larger 20-rotor device, neither of which was ever used during WWII. Why would they have done this? Was it arrogance on their part, "knowing" that Enigma codes were unbreakable?
In 1932 the Japanese introduced a high-level code designated "RED" which was employed for Consular traffic, and subsequently broken by the Americans.
The Japanese had obtained an Enigma machine from Germany, and decided to use the same principle to encode their messages. Rather than using rotors operated by keypresses from the keyboard, they employed electro-mechanical Strowger stepping switches. An electromagnet, acting through a pawl and ratchet mechanism, caused rotating contacts to pass over banks of electrical contacts. The overall machine, although constructed differently, was equivalent to a four-rotor Enigma with electric typewriters on each side. A message was entered on one typewriter, and printed out, encoded, on the second. Although this eliminated some errors in copying an encode from illuminated light bulbs, the weight of the stepping switches and typewriters made it far less portable than the German field Enigma. The Japanese machine was called "97-shiki o-bun in-ji-ki, ("alphabetic typewriter," where 97 referred to Japanese year 2597, 1937 in western dating) or informally "J." The code it produced was called "PURPLE" by the Americans.
The Japanese, more helpful than the Germans, frequently started their messages with "I have the honor to inform your excellency ...". This known correspondence between letters in the coded message and the corresponding plaintext afforded a toehold into breaking the code. The Americans had broken the previous code "Red," and many Japanese mistakes helped them solve "Purple". Operator errors, transmission of exactly the same message in both Red (which had been broken) and Purple codes, using stylized names and addresses, and the use of the same keys for a month, shuffled every 10 days, allowed the Americans to discover the "rotor" wiring and build an analog of the Japanese machine.
It was not that easy; William Friedman, mainly responsible for the effort, suffered a nervous breakdown (some sources claim that the victory was due mainly to Friedman's team). Apparently, he had followed the same analytical route as the Poles, but independently. Incredibly, he had decided to build his "Purple analog" from stepping switches also, which were readily available as stock telephone exchange equipment. The first successful Purple decode was sent to Washington in August, 1940. The Americans could now read the Japanese diplomatic code, but ran into a problem in obtaining messages. Section 605 of the Federal Communications Act of 1934 prohibited wiretaps and the interception of messages between the U.S. and other countries. Most of the Japanese traffic went by cable, not radio, and American cable companies at first refused to hand over messages!
"Magic" was a general term for breaking all Japanese codes, which included:
RED - Supplanted by Purple in 1939.
PURPLE - A high-level machine cipher used at the embassy level.
TSU (J-19) - a consular hand system code.
OITE (PA-K2) - another hand system.
JN-25 - The Japanese Naval code, broken in 1942
BAKER 9 - Replaced JN-25 in May, 1942..
There were also ten other abbreviation codes, of no intelligence value.
Having decoded Japanese messages, the Americans then had to get them to Washington. Presumably the Japanese were also monitoring American traffic, and if they found that their messages were being relayed by the Americans, they might change their coding methods.
Somehow, the Germans found out that the Americans were decoding Japanese messages, and passed this information on to Tokyo. The cryptanalysts held their breath, but incredibly, the Japanese did not change their codes.
By the end of 1941 the Americans were regularly reading Japanese diplomatic codes. Ominously, five days before Pear Harbor, messages between the Japanese homeland and their various embassies were ordering code books to be burned and encoding machines destroyed.
The Americans decoded a 14 part message directed to the Japanese Embassy in Washington. A short message followed, directing that all fourteen parts were to be delivered to the Japanese Ambassador, who would present it to the State Department at 1 p.m. on Sunday, Dec. 7. Due to the secret nature of the message, it was typed up by Japanese Embassy officials instead of clerks. The officials, somewhat less than perfect typists, were force to re-type them over and over again. The fourteenth part of the message had not been typed up by one o'clock; in fact the Japanese Envoys did not arrive at the State Department until 2:05 p.m. They were half an hour late; the well-timed attack on Pearl Harbor had commenced at 1:25 p.m. Washington time (7:55 a.m. in Honolulu). Ironically, the Americans received the message before the envoys did!
Most authors contend that if part 14 of the message from Japan to the
United States had been delivered before the Pearl Harbor attack,
between Japan and the U.S. would have been "legally declared". Among other
nations, Japan, Italy
and Germany were signatories to the Hague Treaty of 1907. One of the
conditions they agreed to was:
"The Contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a reasoned declaration of war or of an ultimatum with conditional declaration of war."
Those three nations ignored that stipulation (Italy invading Ethiopia; Japan entering Manchuria; and Germany invading Poland). Hitler did declare war on the United States, however.
The last paragraph of the 14th part reads as follows:
"The Japanese Government regrets to have to notify hereby the American Government that in view of the attitude of the American Government it cannot but consider that it is impossible to reach an agreement through further negotiations."
Half an hour might be considered "previous", although certainly not in the spirit of the Hague Convention. The wording definitely doesn't appear to be an "explicit" Declaration of War, even if it had been delivered on time.
The full text of the Hague convention can be found at Hague III, and of "Part 14" at Part 14.
Did the United States know about the attack on Pearl Harbor ahead of time, as some theorists conclude? Probably not. The Japanese took great pains to hide the movements of the attacking fleet. They even left their radio operators behind, continuing to transmit from shore in the event their "fists" would be recognized. Complete radio silence was maintained. There was no question that the Japanese were on the move, but no indication of their target. Indeed, there would be no reason for them to radio their intentions to anyone. There were, of course, indications that Hawaii might be their goal, but there were many other conflicting bits of information as well.
The United States was not prepared for war. Specifically, there was no system for the efficient dissemination of intelligence, such as the British and Germans had. Perhaps most dangerous of all, Americans were imbued with a sense of false security. Immediately following the Pearl Harbor attack the United States declared war on Japan. Although the United States had failed to come to the aid of Great Britain, the only nation actively fighting the Germans, Great Britain immediately declared war against Japan. On December 11 Hitler declared war on the United States.
Espionage and Internment
Through hundreds of Magic decodes, the Americans were cognizant of a very real threat of widespread espionage and sabotage on their west coast, including the Panama Canal. It was learned that Spain was being paid for espionage in the U.S., the information presented to the Japanese Ambassador, who relayed it to Tokyo, encoded in Purple. Feb. 19, 1942 President Roosevelt signed executive order No. 9066, which ordered immediate evacuation of over 100,000 residents of Japanese descent away from coastal areas.
A change in the perception of the Japanese after World War II, plus a strong lobbying effort by the Japanese community, resulted in the Commission on Wartime Relocation and Internment of Civilians holding hearings in 1983. Magic decodes spelling out the dangers of espionage and sabotage were suppressed, and in 1988 awarded $20,000 and an official government apology to all the evacuees. More details can be found in David Lowman's Magic.
The Italians were firmly entrenched in Libya, with some 200,000 troops. On June 10, 1940 Italy declared war on Great Britain, and proceeded to invade Egypt in September. Gen. Sir Archibald Wavell, Commander in Chief of British forces in the Middle East, was pitifully short of resources. On the other hand, the Italians were overcautious, and missed many opportunities. The British counter-offensive in December cleared Egypt of Italian forces, and 130,000 prisoners were taken.
In February, 1941 Field Marshal Erwin Rommel (soon to be known as "The Desert Fox") arrived in Libya. Wavell was informed of this event from Ultra, but although he got the facts, he did not interpret them correctly, and Rommel managed to push the British forces back to Egypt.
The British had a secret weapon Rommel knew nothing about: Ultra intelligence, which revealed the Germans' strength and plans in the minutest detail. One German operator in Algiers helpfully transmitted "Nichts zu melden" (nothing to report) faithfully every day, using the key in effect for that day.
Rommel had his own intelligence from B-Dienst, which kept him well-informed of British plans.
At first, the Allies could only assure an effective withdrawal from Rommel's superior forces. Field Marshal Albert Kesselring, chief of German forces in the south, was installed in Rome, from where he helped Rommel direct his battles.
American codes and security precautions were pitifully inadequate. This often hurt others more than the U.S. In August, 1941 an Italian spy employed at the American Military Attaché's office in Rome obtained a key to the safe. He was able to steal a copy of America's "Black" code (so named from the bonder color)
, photograph it, replace it undetected, and pass it along to the Germans.
American Military Attaché Colonel Bonner Frank Fellers toured British battlefields in Africa. His complete reports to Washington of British strength, positions, supplies, morale, etc. were decoded by the German E-Dienst and passed on to Rommel. One message caused great consternation to the Germans, an American intercept referring to shipments of "gas." The Germans, not realizing that gas was Americanese for petrol, anticipated biological warfare!
By the end of 1941 the war was not going well for the Allies, but there was a glimmer of hope. The United States was contributing its industrial might to the manufacture of vital war materiel.
The Allies were reading the Axis codes with some regularity, but the Germans were reading Allied codes as well. It was going to be a long war.