above A US Navy ‘bombe’, based on Alan Turing’s design, being operated by a member of the US Navy women’s reserves, known as WAVES.

Churchill’s American arsenal: the special relationship that won World War II

In a new book, Larrie D Ferreiro explains how a special relationship between British and US combat scientists and engineers produced the innovations that won the Second World War.


Shortly after midnight on the morning of 28 February 1942, the men of 2nd Paratroop Battalion, C Company, dropped through a small opening in the floor of the fuselage of their modified bombers, floating down and landing in a foot of fresh snow on level ground, about 600 yards from their intended target near the town of Bruneval on the Normandy coast. A perfect drop, despite heavy anti-aircraft fire. Led by Major John Frost, who would later distinguish himself at Arnhem during Operation Market Garden (and who would eventually be portrayed by Anthony Hopkins in the movie A Bridge Too Far), the paratroopers fought off German troops while they captured and dismantled a German Würzburg air-intercept radar system. But when they arrived at the designated evacuation point on the beach below the cliffs, there was no sign of the Royal Navy. Frost sent up red signal flares, which also gave away their position to the Germans. Thankfully, the six landing craft drew up to the beach before the counter-attack could begin, and radar scientist Donald Priest was able carefully to stow the captured gear. The evacuation was messy but successful – for the first time, British scientists would have a good look at German radar, and begin to devise the means to defeat it.

left Winston Churchill watches the arrival in Britain
Winston Churchill watches the arrival in Britain of the first US B-17 ‘Flying Fortress’, on 6 June 1941. Image: Library of Congress

The Second World War was fought not only with guns, ships, and aircraft, but also with a wide range of new technologies that were just being invented when the conflict began. As the American scientist Vannevar Bush pointed out, it was ‘the first war in human history to be affected decisively by weapons unknown at the outbreak of hostilities’. Bush was the head of the Office of Scientific Research and Development (OSRD), a massive United States federal agency established in 1940 by President Roosevelt that mobilised American scientists and engineers to develop those ‘unknown’ weapons. Almost as soon as OSRD was established, a British team – called the Tizard Mission after its leader, Henry Tizard – arrived in the US to offer the hard-won fruits of its science and technology, developed over a decade of preparing for war with Germany. The OSRD scientists immediately recognised the benefits of these British inventions, such as airborne radar and the proximity fuse, and established offices in London and across England so that the two nations could cooperate on their development.

By the time of the Bruneval Raid, the United States had entered the war, and OSRD scientists and engineers were working side by side with their British counterparts to get these new weapons to the front lines. When the Würzburg radar was examined, British scientists at the Telecommunications Research Establishment (TRE, where Donald Priest worked) figured out that they could fool it by scattering from aircraft clouds of aluminium foil. These reflected back to the radar, which would pick up the large returns and confuse them with the actual Allied aircraft. But TRE was unable to manufacture the thin slivers of foil – later nicknamed ‘chaff’ – in sufficient quantities, so they turned to OSRD’s radar laboratories at the Massachusetts Institute of Technology (MIT) and Harvard, as well as to American industrial giants such as Reynolds Metals Company. Together, they designed and built machines that spewed out almost a million pounds of chaff per month, equipping all the British and American bombers after 1943. German radars were indeed fooled – during one of the early bomber raids, British radio intercept operators heard the German controllers tell their fighter pilots to break off because the Allied bombers were ‘multiplying themselves’. Throughout the war, chaff kept German air defences on the back foot, cutting Allied bomber losses by up to two-thirds and allowing them to attack their target successfully.

left A daring British raid on a property at Bruneval in northern France led to the capture of a German Würzburg radar system [at the left of this picture] on 28 February 1942.
A daring British raid on a property at Bruneval in northern France led to the capture of a German Würzburg radar system [at the left of this picture] on 28 February 1942. Image: MIT

Fight in the air

Germany was not the only nation to use land-based radar early in the war. By 1940, the United States had built the SCR-270 (which later detected the inbound Japanese aircraft 45 minutes before the attack on Pearl Harbor) and Britain had the Chain Home system (which directed fighters against the Nazi bombers in the Battle of Britain and the Blitz). But all these radar systems were too large to fit on aircraft, and thus were only employed for defence. In the early years of the war, the only way to attack the Nazi war machine was by air, and even after overcoming German air defences, bombers could not accurately hit strategic targets at night or through the often-overcast skies of Europe. The Allies needed a radar system small enough to fit into bombers, so they could go on the offence, day and night, in all weathers.

When Winston Churchill gave his ‘fight on the beaches’ speech, in June 1940 after the Dunkirk evacuations, he evoked two important themes: that Britain would fight with ‘growing strength in the air’, and that he was certain that the ‘New World’ (the US) would eventually enter the fray. Just weeks later, in an effort to bolster British scientific know-how with American industrial might, he authorised the Tizard Mission to travel to the US with what one historian there described as ‘the most valuable cargo ever brought to our shores’. Inside a nondescript tin box was the cavity magnetron, a small copper cylinder that today is at the heart of every microwave oven, but was then a technological breakthrough. Invented by British scientists at the University of Birmingham, it effectively miniaturised the massive radars (such as those in Chain Home) to a size that could fit inside an aircraft. It also operated at a short-enough wavelength that it could discern cities and factories from the surrounding landscape. OSRD realised that the cavity magnetron was a breakthrough in radar, and immediately established the ‘Radiation Laboratory’ (or Rad Lab) at MIT to improve it, while Harvard stood up the Radio Research Laboratory (RRL) to develop counter-measures for the air war. OSRD put in orders with Bell Telephone factories, too, where armies of mostly women workers mass-produced tens of thousands of cavity magnetrons for both British and American use.

below left The British scientist Henry Tizard [centre] with cavity magnetrons at MIT’s ‘Radiation Laboratory’, or Rad Lab. below right A Lancaster bomber dropping thin slivers of foil known as ‘chaff’ over the German city of Duisburg.
The British scientist Henry Tizard [centre] with cavity magnetrons at MIT’s ‘Radiation Laboratory’, or Rad Lab. IMAGE: Creative Commons

It was never the case of America simply building British inventions. OSRD became the focal point for scientific cooperation with the British, establishing a London Mission to coordinate R&D activities on both sides of the pond. After the United States entered the war in December 1941, the two nations established British branches of the Rad Lab and RRL, both located alongside TRE deep in the English countryside. American and British scientists and engineers (notably Isidor Rabi and Bernard Lovell, both of whom became science leaders during the Cold War) worked side by side to develop, test, and deploy radars powered by cavity magnetrons.

One of the most important results of their cooperation was the H2S radar, carried by the Lancaster, B-17 Flying Fortress, and other bombers in order to ‘see’ ground targets through clouds or even at night. This allowed the bombers to hit strategic targets such as oil- production facilities and factories more accurately, bringing the fight to the enemy. At every step, Allied combat scientists were in the field, training and working with front-line forces on radar and chaff, among many other weapons. After the war, Hermann Goering, along with other high-level Nazi officials, confirmed the effect of radar-directed bombings on the German war effort. According to Albert Speer, the man who had mobilised Germany’s war economy, they had ‘caused the breakdown’ of the country’s entire armaments industry.

Rebecca/Eureka transponding radar

‘Invention is the mother of necessity’ said the historian of technology Melvin Kranzberg, turning Plato’s dictum on its head, and this was the case with the development of the Rebecca/Eureka radio beacon system. Soon after Britain’s Telecommunications Research Establishment had developed the cavity magnetron radar [see main text] in 1940, its scientists realised it could be used to help the targeting of parachute drops. They demonstrated the two-part Rebecca/Eureka system to the Special Operations Executive (SOE), which immediately saw that it could be used to pinpoint agents behind enemy lines: ‘Rebecca’ (the name of the airborne transceiver and antenna) derives from the phrase ‘Recognition of beacons’, while ‘Eureka’ (the name of the ground-based transponder) comes from the Greek for ‘I have found it!’. The American Army Air Force got wind of it and asked for thousands of them. British engineers were sent to the American electronics company Philco, which worked around the clock to build units for the upcoming invasions of Italy and France. On D-Day, Allied ‘pathfinder’ paratroopers deployed Rebecca/Eureka beacons to guide airborne troops and gliders to their landing zones: despite German defences and foul weather, they hit more than 80 per cent of their intended targets.

9A Lancaster bomber dropping thin slivers of foil known as ‘chaff’ over the German city of Duisburg. Image: Alamy

Fight on the landing grounds

Although the cavity magnetron was ‘the most valuable cargo’ carried by the Tizard Mission in 1940, a close second place was taken by the proximity fuse. Even before his mission to the US, Henry Tizard led a team that was developing novel ways of shooting down enemy aircraft. To date, anti-aircraft artillery (like the Vickers 3.7-inch gun and the American 90mm gun) fired shells that were fused to burst at specific altitudes, but this required many thousands of rounds for a single kill. The most promising new technology involved fitting anti-aircraft shells with tiny radars that would detect when it was close to a target, and then explode. When the Tizard Mission arrived in the US, the basic principles of the proximity fuse had been worked out by British scientists William Butement and John Cockcroft, the latter of whom showed it to the Americans. OSRD was intrigued by the results, and Vannevar Bush assigned one of his own scientists, Merle Tuve, to form ‘Section T’ to develop the technology with British assistance.

Section T (for Tuve) had to figure out how to manufacture miniature radio vacuum tubes that could fit in an artillery shell, but were also rugged enough to survive being shot from the barrel of a gun. Tuve transformed from a bench scientist to a hard-driving manager up against an impossible-to-meet deadline. His first rule was, ‘I don’t want any damn fool in this laboratory to save money. I only want him to save time.’ At the beginning, he scrounged for supplies (buying gunpowder from a local florist) and beseeched friends to use their farms and fields to test-fire the shells, counting on a Chesapeake Bay Retriever to find them. Tuve, frustrated by the lack of funds and priority, wrote a pointed memo to OSRD stating, ‘Time is shorter than we think.’ The date on the memo was Saturday 6 December 1941 – the day before Pearl Harbor.

LEFT A Lancaster silhouetted against flares and smoke during the attack on Hamburg on 30/31 January 1943, the first occasion on which H2S radar was used to navigate the bombing run.
A Lancaster silhouetted against flares and smoke during the attack on Hamburg on 30/31 January 1943, the first occasion on which H2S radar was used to navigate the bombing run. Image: Alamy

The entry of the United States into the Second World War dramatically boosted the proximity-fuse programme. Section T became the Applied Physics Laboratory at Baltimore’s Johns Hopkins University (recently famous for its interplanetary mission to Pluto), and grew to over 800 staff. Both the American and British navies and armies, facing onslaughts of German and Japanese air-attacks, clamoured for the proximity fuse to be brought into service. By the autumn of 1942, tests were so successful that proximity fuses were shipped to the Pacific theatre, where gunnery crews were trained under the watchful eyes of combat scientists, such as James Van Allen (discoverer of the Van Allen Belt), who was awarded four battle stars for his work. During the latter years of the war, the proximity fuse was credited with half of all Japanese aircraft downed.

The arrival of the proximity fuse in Britain coincided with the V-1 attacks in June 1944, immediately after D-Day. OSRD combat scientists such as Ed Salant worked tirelessly to train artillery crews on the fuses. In the first weeks, only a few V-1s were shot down; by August 1944, however, the rate was 95 per cent destroyed. In the European theatre, the proximity fuse was not deployed until December 1944 for fear of it falling into Nazi hands. Once again, Salant was on the front lines helping troops deploy it with devastating effectiveness. General George S Patton later penned several notes to the US War Department and the Applied Physics Laboratory, stating that ‘the new shell with the funny fuse… won the Battle of the Bulge for us’.

ABOVE The aftermath of a V1 strike in Upper Norwood, south London. By August 1944, however, the advent of the proximity fuse meant that 95 per cent of V1s were destroyed.
The aftermath of a V1 strike in Upper Norwood, south London. By August 1944, however, the advent of the proximity fuse meant that 95 per cent of V1s were destroyed. Image: Wikimedia Commons

‘Donald Duck’ Sherman tanks

Allied commanders planning the June 1944 D-Day invasion knew that, before landing boats and troops hit the beaches of northern France, the guns of the Nazi coastal defences known as the Atlantic Wall would have to be neutralised by tank artillery. A Hungarian-British engineer named Nicholas Straussler had already developed special modifications (propellers and flotation devices) that would allow tanks to ‘swim’ to shore. In 1943, Eisenhower’s staff asked Straussler to send plans and engineers to America to fit these modifications to US Sherman medium tanks. With a briefcase of drawings handcuffed to his wrist, Straussler’s right-hand man John E Whatmough arrived at the Lima Tank Depot in Ohio to oversee the modification of 350 Duplex-Drive (DD) Shermans, which were quickly nicknamed ‘Donald Duck tanks’. By March 1944, the tanks were in Britain, to be used by all Allied landing forces. Despite problems on one section of Omaha Beach, over three-quarters of the DD tanks got to shore. ‘They saved the day,’ said one infantry commander. ‘They shot the hell out of the Germans and got the hell shot out of them.’

Fight on the seas and oceans

The 2014 film The Imitation Game (starring Benedict Cumberbatch as the mathematician Alan Turing) dramatised the Bletchley Park codebreaking of U-boat Enigma messages, which turned the tide of the Battle of the Atlantic. The film took many liberties for narrative purposes – most notably with the fact that, by 1944, almost all of those Enigma intercepts were deciphered in Washington, DC, using American-built ‘bombes’ based on Turing’s design, though improved and made more powerful by an electrical engineer named Joe Desch who worked at National Cash Register (NCR) in Dayton, Ohio.

The primary Allied strategy for the Battle of the Atlantic, unlike during many other campaigns, was not to seek out and destroy enemy forces, but to avoid them whenever possible. Even before the United States entered the war, Admiral Karl Dönitz’s U-boats were threatening the merchant convoys that kept Britain armed and fed. Dönitz coordinated his wolfpacks with a steady stream of encrypted radio messages that he thought could not be broken. He never realised that the Enigma devices used to encrypt messages had been smuggled to Britain by Polish intelligence agents, along with ‘bombes’ – machines that could decrypt the Enigma traffic. By May 1940, Turing’s team, using updated Enigma machines and codebooks that had recently been captured, built new bombes that could read U-boat messages, allowing the Royal Navy to order convoys to avoid the wolfpacks.

above A US Navy ‘bombe’, based on Alan Turing’s design, being operated by a member of the US Navy women’s reserves, known as WAVES.
A US Navy ‘bombe’, based on Alan Turing’s design, being operated by a member of the US Navy women’s reserves, known as WAVES. Image: Creative Commons

In 1942, the German Navy introduced a more powerful Enigma machine that suddenly rendered Bletchley Park deaf and blind. The British allowed their American allies complete access to the existing Bletchley bombes, in return for help in creating and mass-producing a more powerful machine. The US Navy assigned this ‘Ultra’ project (its security designation) to NCR, where Joe Desch had already produced electronic calculators for the Manhattan Project to use in developing the first nuclear weapons. Ultra restrictions were so onerous that Desch was accompanied by a Navy officer at all times, including in his house while he slept. In September 1942, Turing visited Desch in Ohio and inspected the improved bombe, which soon entered mass-production. NCR established a special production line in Dayton almost fully staffed by the US Navy women’s reserves known as WAVES, who meticulously soldered and assembled more than 100 bombes, each weighing 5,000 pounds, for use by both the British and American intelligence services.

All the NCR bombes, both British and American, were operated by WAVES in a special Navy annex in Washington, DC. Each day, Wrens (members of the UK’s Women’s Royal Naval Service) at Bletchley Park sent intercepted U-boat messages to the US Navy annex, where WAVES decoded them and sent them back across the Atlantic. By March 1944, with D-Day planning in full swing, the Allies agreed that the US Navy would decrypt all further U-boat message traffic, leaving the British (aided by on-site American codebreakers) to focus on German Army and Air Force messages for the invasion of Europe. By the time the invasion of Normandy began, Allied convoys were crossing the Atlantic almost unimpeded by U-boats, testament to the effectiveness of the British and American servicewomen who helped keep them out of harm’s way.

below Vannevar Bush was head of the Office of Scientific Research and Development (OSRD), the US federal agency established to develop ‘unknown’ weapons.
Vannevar Bush was head of the Office of Scientific Research and Development (OSRD), the US federal agency established to develop ‘unknown’ weapons. Image: Library of Congress

The Alsos Mission

The most famous mission undertaken by British and American combat scientists was codenamed Alsos, after the Greek word for ‘grove’. It was initiated by the Manhattan Project (the research and development project that produced the first nuclear weapons) to determine whether the Nazi regime had the atomic bomb. Since most of the early discoveries in nuclear fission were German, it was assumed that they were developing a bomb of their own. When Allied troops landed in Italy (in September 1943) and Normandy (in June 1944), Alsos followed in their wake to visit German sites and round up their scientists. Alsos was led by US Army military intelligence officer Boris Pash and atomic scientist Sam Goudsmit, and included another scientist, Gerard Kuiper, who later became a celebrated astronomer. In March and April 1945, as Allied troops crossed the River Rhine, the Alsos team found a primitive atomic reactor, and after a fierce firefight led by Pash in the Bavarian Alps, managed to capture its chief scientist, Werner Heisenberg. Goudsmit and the other Allied scientists determined that the German atomic programme was nowhere near able to make a bomb.

The New World steps forth

While the cavity magnetron was being developed at the University of Birmingham in early 1940, two scientists there, Rudolf Peierls and Otto Frisch, were prohibited from working on such a top-secret project because they were émigrés, refugees from the Nazi regime. Instead, they were assigned a far-fetched project to confirm recent German discoveries concerning the fission of Uranium-235. They soon determined that just a few pounds of this isotope could produce an explosive yield of many thousands of tons of TNT, which meant that an atomic bomb could fit on a bomber and deliver untold destruction to the heart of Germany. John Cockcroft of the Tizard Mission brought only a few scraps of information to the Americans, because it was still unconfirmed, but by the summer of 1941 British science had advanced so much that Churchill authorised an atomic bomb programme under the innocuous name ‘Tube Alloys’. Fearing that the Germans were already working on an equivalent, some British scientists leaked word of the project to the OSRD London Mission, hoping to tap into the vast might of US science and industry.

Vannevar Bush did not reveal the leaked information to Roosevelt until the findings were confirmed officially in October 1941. Roosevelt ordered OSRD to establish a cooperative research programme with Britain, which like other such efforts, sped up dramatically after Pearl Harbor. The scale of the programme became so vast that Roosevelt established a separate atomic bomb programme under the Army Corps of Engineers, codenamed the ‘Manhattan Project’. At first, its leader Lieutenant General Leslie Groves was wary of British involvement, but after heated diplomatic discussions between Churchill, Bush and Roosevelt, a cooperative arrangement was reached in 1943 that allowed British scientists to move from Tube Alloys to the Manhattan Project.

right The Alamogordo test of the first atomic bomb on 16 July 1945. According to one observer, it was as if someone had ‘turned the sun on with a switch’.
The Alamogordo test of the first atomic bomb on 16 July 1945. According to one observer, it was as if someone had ‘turned the sun on with a switch’. Image: Wikimedia Commons

Three dozen British researchers (including Peierls and Frisch) spread out over multiple Manhattan Project sites, including Los Alamos (in New Mexico) and Oak Ridge (in Tennessee). Work progressed quickly to develop the bomb, continuing after Germany’s defeat in April 1945. Frisch was in New Mexico for the Alamogordo test of the first atom bomb that July, which he described as if someone had ‘turned the sun on with a switch’. Within weeks, B-29 bombers, each fitted with H2X radar (a development of H2S), chaff, and dozens more devices codeveloped by Britain and the US, dropped two atomic bombs on Japan.

Japanese delegates signed the Instrument of Surrender aboard the battleship USS Missouri on 2 September 1945. Anchored in Tokyo Bay, they were surrounded by more than 200 Allied ships, mainly from the US and UK. They had worked and fought side by side, in what Churchill was already referring to as a ‘special relationship’. Moreover, the collaboration between the two countries’ combat scientists in creating ‘weapons unknown at the outbreak of hostilities’, as Vannevar Bush had put it, had been crucial to victory. It marked the beginning of international scientific cooperation that today is deployed against modern threats of disease, poverty, and climate change – not just for allied nations, but, as the Apollo astronauts once said, for ‘all mankind’.

Larrie D Ferreiro is an engineer, historian, and author of award-winning books including the 2017 Pulitzer Prize finalist in history Brothers at Arms: American independence and the men of France and Spain who saved it. His latest book, Churchill’s American Arsenal: the partnership behind the innovations that won World War II, is out now (OUP, hardback).