The Tizard Mission

On 14 August 1940, the day after the great German “Eagle Day”, Sir Henry Tizard, Rector of Imperial College London and for some years the British air force’s most important scientific adviser, left Britain to cross the Atlantic. He was leading a delegation officially called the British Technical and Scientific Mission, which went down in history as the Tizard Mission. Its task was without precedent: Britain, fighting Germany alone, was to show the United States, a neutral country, its most closely guarded military secrets, without demanding anything in return in advance. The most precious of them was a small copper device which, a few weeks later, taken out of a black metal box, astounded American physicists: the cavity magnetron, a source of radio waves that made it possible to fit radar into an aircraft.

It is often said that on 14 August Tizard left for the United States and handed the Americans secrets including the magnetron. The sources allow this to be made more precise. That day Tizard and an RAF officer, Group Captain F. L. Pearce, flew by Short Empire flying boat to Montreal, and the next day they were in Ottawa for talks with the Canadian National Research Council. Tizard reached Washington on 22 August. The rest of the mission, with the box of documents and the magnetron, sailed from Liverpool only at the end of August (sources give 29 or 30 August), and the magnetron itself was shown to the Americans on 19 September.

Why the British gave their secrets away

In the summer of 1940 British scientists had more promising inventions in hand than the country could exploit. Industry, bombed and overloaded with the production of fighters, ammunition and warships, had no spare capacity to perfect and mass-produce devices that would be useful only in a year or two. The United States had what Britain lacked: an enormous industry untouched by war, the laboratories of the great electrical companies, and money. After the fall of France Washington began to rearm rapidly: in July Roosevelt asked Congress for further billions for defence, and in June the National Defense Research Committee (NDRC) had been set up under the engineer Vannevar Bush to harness science to rearmament.

Tizard believed that the most effective course was simply to give the Americans everything the British knew and to make use of American factories. His reasoning was that the secrets would grow old anyway, and that working on them together would bring the two countries closer. The ground was prepared by the physiologist and Nobel laureate Archibald Vivian Hill, a member of Tizard’s committee, who had been sent to the British Embassy in Washington in the spring of 1940 and reported that the Americans were ready to co-operate. The ambassador, Lord Lothian, put a proposal for an exchange of information to the American government, and before the end of July President Franklin Delano Roosevelt had accepted it.

In London the idea met resistance. The pioneer of British radar, Robert Watson-Watt, did not want to give away the fruits of his work, and the Prime Minister, Winston Churchill, hesitated for a long time, fearing that the secrets would leak or that America, while neutral, would give nothing in return. He gave his consent only after several weeks, in the summer of 1940. The choice of Tizard to head the delegation also had a hidden side. When Churchill became Prime Minister, the influence on science policy of his scientific adviser Frederick Lindemann – once Tizard’s friend, and since the mid-1930s his bitter rival – grew sharply, and Tizard, who in June 1940 had lost the argument over whether the Germans were guiding their bombers by radio beams (the Knickebein (PL) system, described earlier in the Oslo Report, among other places), soon afterwards resigned as adviser to the Chief of the Air Staff. He remained adviser to Lord Beaverbrook’s Ministry of Aircraft Production. The mission across the ocean was a task worthy of his experience and at the same time, as his biographers note, a convenient way of removing him from the centre of decision-making.

The black box

Besides Tizard, the delegation numbered six people: one representative each of the army (Brigadier F. C. Wallace), the navy (Captain H. W. Faulkner) and the air force (Group Captain F. L. Pearce); the nuclear physicist John Cockcroft, Assistant Director of Scientific Research at the Ministry of Supply; the radar specialist Edward George “Taffy” Bowen; and a secretary from the Air Ministry, Arthur Woodward-Nutt. All the documents were gathered in a single lockable metal deed box, of the kind in which solicitors’ offices kept title deeds. According to the participants’ accounts, if the ship were torpedoed it was to be thrown overboard and sink to the bottom.

The box contained plans and descriptions of almost everything British military science was working on: Chain Home early-warning radars; airborne radars for detecting submarines and aircraft; the proximity fuze, which was to detonate next to an aircraft without hitting it (the idea of the engineer Alan Butement); rockets; gyroscopic gunsights; anti-aircraft predictors; self-sealing fuel tanks; new explosives; submarine detection equipment (asdic); and Frank Whittle’s jet engine. Cockcroft was also authorised to discuss British work on uranium. In March 1940 two refugees from the Reich working in Birmingham, Otto Frisch and Rudolf Peierls, had calculated in a memorandum that a bomb of pure uranium-235 would need a few kilograms of the metal rather than tons, and in April a committee, later called MAUD, had been set up to look into it.

The most important thing, however, was the one object in the box. In February 1940, in Mark Oliphant’s laboratory at the University of Birmingham, John Randall and Harry Boot had built the cavity magnetron: a valve in which electrons circling in a magnetic field set up oscillations in cavities drilled into a copper block. The palm-sized device produced pulses with a power of several, and soon a dozen or more, kilowatts at a wavelength of 10 centimetres – hundreds of times more than any previously known source of such short waves. A short wavelength meant a small aerial, a sharper picture and the ability to detect small targets, such as the conning tower of a surfaced submarine. In the summer of 1940 the GEC company at Wembley made twelve trial examples. Bowen took number 12 across the ocean.

The secrets travelled with a very British mixture of care and improvisation. The box spent a night under Bowen’s bed in a London hotel; in the morning it was tied to the roof of a taxi, and at Euston station a zealous porter whisked it away from under Bowen’s nose, so that for a moment he lost sight of it. At Liverpool a military escort took charge of the box. The delegation sailed in the liner Duchess of Richmond, which was also carrying troops, and landed at Halifax in Canada on 6 September. On 12 September the whole mission gathered in Washington, where the Shoreham Hotel became its office.

Talks in Washington

Tizard had spent two weeks preparing the ground. At the end of August he met Bush (on 31 August, according to most accounts) and arranged a series of talks with the individual sections of the NDRC. These began cautiously, because the American army and navy agreed to disclose their secrets to the British only on 12 and 16 September and did not expect to learn anything. The first talks seemed to confirm this: the British described their Chain Home stations and learned that the US Navy had a very similar long-range detection radar, the CXAM. The Americans admitted, on the other hand, that their work on a 10-centimetre radar had stalled because they lacked a sufficiently powerful transmitter.

The breakthrough came on 19 September at a meeting with the NDRC’s Microwave Committee, chaired by Alfred Lee Loomis, a banker, amateur physicist and patron of science. In his suite at the Wardman Park Hotel in Washington, Bowen and Cockcroft showed the magnetron and gave its power output. The Americans were stunned. Tests at Bell Labs in early October confirmed that the device produced about 10–15 kilowatts, many times more than the best American valves at a wavelength several times longer. An X-ray examination produced a surprise: number 12 had eight cavities, whereas the accompanying drawings showed six. It turned out that GEC had built several trial versions, and the eight-cavity one had gone to America. It was this one that the Americans copied. On 28–29 September members of the mission met the Microwave Committee at Loomis’s estate at Tuxedo Park near New York and set priorities: first place went to an airborne radar for night fighters.

The exchange was not entirely symmetrical. The British asked for the Norden bombsight, the pride of American technology, but Roosevelt refused. Tizard took this calmly and asked only for the bombsight’s dimensions, so that space could be left for it in British bombers. He discussed the jet engine with Bush and with NACA’s director of research, George Lewis, but he knew few technical details, and only in 1941 did the Americans grasp how far ahead of them Whittle was. In the talks on uranium the delegation visited Enrico Fermi at Columbia University, where fission had been studied since January 1939, and the Canadian physicist George Laurence in Ottawa. Fermi was sceptical about a bomb, and Cockcroft judged that American nuclear work, begun after Einstein’s letter to Roosevelt, was less advanced than the British.

Tizard returned to London at the beginning of October (on 8 October, according to some accounts). Leadership of the mission passed to Cockcroft, who went on to Canada and returned home in December. Bowen stayed in America for several years as a liaison officer.

What grew out of it

Co-operation on radar bore fruit fastest. The NDRC decided that a separate, large laboratory was needed to exploit the magnetron. On 17 October it was agreed that it would be set up at the Massachusetts Institute of Technology; on 25 October the contract was approved; and on 11 November 1940 the first scientists gathered in the new laboratory. To mislead, it was called the Radiation Laboratory, as if it dealt with nuclear physics. It was headed by Lee DuBridge, and at its peak almost 4,000 people worked there. The Rad Lab designed about a hundred types of radar, among them the SCR-584 gun-laying radar, which in 1944 helped to shoot down V-1 flying bombs over England, bomber radars for aiming through cloud, and the LORAN navigation system. Magnetrons were mass-produced by American firms, above all by Bell. Centimetric radars in patrol aircraft played a great part in the victory over the U-boats in 1943.

From the British idea of a proximity fuze the Americans, under the physicist Merle Tuve, developed a radio fuze for artillery shells. The first aircraft brought down with it was downed by American naval guns in the Pacific in January 1943, and in 1944 these fuzes, supplied to the British, contributed to the defence against the V-1. The plans of Whittle’s engine, handed to the Americans in 1941, enabled General Electric to build the first American jet engine. It powered the Bell P-59 Airacomet fighter, first flown in October 1942.

On the atomic bomb the mission did not bring an immediate breakthrough. On its return the delegation took the view that the work on slow neutrons in France, America and Canada was of significance chiefly for peaceful purposes. Only the MAUD Committee’s report of July 1941, which judged a bomb feasible within the war, convinced Bush and Roosevelt. Still, the channels of contact opened in 1940 allowed that report to be passed on quickly and led to British scientists taking part in the Manhattan Project.

Significance

The Tizard Mission came at a moment when the air battle over England was being decided and talks were under way in Washington on handing American destroyers over to the British. The British gave away their secrets before they had received anything in return and before they knew whether the United States would ever enter the war. In doing so they convinced the distrustful American military that Britain was not a beaten supplicant but a partner with much to offer. On that trust grew the wartime scientific partnership: permanent liaison missions in London and Washington, joint radar and nuclear programmes, and after the war close defence co-operation between the United States, Britain and Canada.

The American historian James Phinney Baxter, the official historian of US wartime scientific research, wrote of the magnetron that the members of the Tizard Mission had brought with it to America “the most valuable cargo ever brought to our shores”. Although the phrase is sometimes regarded as an exaggeration, few single objects changed the course of the war so clearly. Centimetric radar, developed from then on jointly on both sides of the Atlantic, gave the Allies the advantage in night air fighting, in the Battle of the Atlantic and in bombing, and the Germans matched it only late in the war, after capturing a British magnetron from a downed bomber in 1943.