Before there was Oppenheimer there was Vannevar Bush

I just saw the movie Oppenheimer.  A wonderful movie on multiple levels.

But the Atomic Bomb story that starts at Los Alamos with Oppenheimer and General Grove misses the fact that from mid-1940 to mid-1942 it was Vannevar Bush (and his number 2, James Conant, the president of Harvard) who ran the U.S. atomic bomb program and laid the groundwork that made the Manhattan Project possible.

Here’s the story.

During World War II, the combatants (Germany, Britain, U.S. Japan, Italy, and the Soviet Union) made strategic decisions about what types of weapons to build (tanks, airplanes, ships, submarines, artillery, rockets), what was the right mix (aircraft carriers, fighter planes, bombers, light/ medium/ heavy tanks, etc.) and how many to build.

But only one country – the U.S. — succeeded in building nuclear reactors and nuclear weapons during the war, moving from atomic theory and lab experiments to actually deploying nuclear weapons in a remarkable 3 years.

Three reasons unique to the U.S. made this possible:

  1. Émigré and U.S. physicists who feared that the Nazis would have an atomic bomb led to passionate advocacy before the government became involved.
  2. A Presidential Science Advisor who created a civilian organization for building advanced weapons systems, funded and coordinated atomic research, then convinced the president to authorize an atomic bomb program and order the Army build it.
  3. The commitment of U.S. industrial capacity and manpower to the atomic bomb program as the No. 1 national priority.

The Atom Splits
In December 1938 scientists in Nazi Germany reported a new discovery – that the Uranium atom split (fissioned) when it hit with neutrons. Other scientists calculated that splitting the uranium atom released an enormous amount of energy.

Fear and Einstein
Once it became clear that in theory a single bomb with enormous destructive potential was possible, it’s hard to understate the existential dread, fear, and outright panic of U.S. and British emigre physicists – many of them Jewish refugees who had fled Germany and occupied Europe. In the 1920s and ‘30s, Germany was the world center of advanced physics and the home of many first-class scientists. After seeing firsthand the terror of Nazi conquest, the U.S. and British understood all too well what an atomic bomb in the hands of the Nazis would mean. They assumed that German scientists had the know-how and capacity to build an atomic bomb. This was so concerning that physicists convinced Albert Einstein in August 1939 to write to President Roosevelt pointing out the potential of an atomic weapon and the risk of the bomb in German hands.

Motivated by fear of a Nazi atomic bomb, for the next two years scientists in the U.S. lobbied, pushed and worked at a frantic speed to get the government engaged, believing they were in a race with Nazi Germany to build a bomb.

After Einstein’s letter, Roosevelt appointed an Advisory Committee on Uranium. In early 1940 the Committee recommended that the government fund limited research on Uranium isotope separation. It spent $6,000.

Vannevar Bush Takes Over – National Defense Research Committee (NRDC)
European émigré physicists (Einstein, Fermi, Szilard, and Teller) and Ernest Lawrence at Berkeley were frustrated at the pace the Advisory Committee on Uranium was moving. As theorists, they thought it was clear an atomic bomb could be built. They wanted the U.S. government to aggressively fund atomic research, so that the U.S. could build an atomic bomb before the Germans had one.

They weren’t alone in feeling frustrated about the U.S. approach to advanced weapons, not just atomic bombs.

In June 1940 Vannevar Bush, ex-MIT dean of engineering; and a group of the country’s top science and research administrators (Harvard President James Conant, Bell Labs President and head of the National Academy of Sciences Frank Jewett, and Richard Tolman Caltech Dean) all felt that there was a huge disconnect. The U.S. military had little idea of what science could provide in the event of war, and scientists were wholly in the dark as to what the military needed. As a result, they believed the U.S. was woefully unprepared and ill-equipped for a war driven by technology.

This group engineered a massive end run around the existing Army and Navy Research and Development labs. Bush and others believed that advanced weapons could be created better and faster if they could be designed by civilian scientists and engineers in universities and companies.

The scientists drafted a one-page plan for a National Defense Research Committee (NDRC). The NDRC would look for new technologies that the military labs weren’t working on (radar, proximity fuses, and anti-submarine warfare. (At first, atomic weapons weren’t even on their list.)

in June 1940 Bush got Roosevelt’s approval for the NDRC. In a masterful bureaucratic sleight of hand the NDRC sat in the newly created Executive Office of the President (EOP), where it got its funding and reported directly to the president. This meant that the NDRC didn’t need legislation or a presidential executive order. More importantly it could operate without congressional or military oversight.

Roosevelt’s decision gave the United States an 18-month head start for employing science in the war effort.

The NRDC was divided into five divisions and one committee, each run by a civilian director and each having a number of sections. (see diagram below.)

Bush became chairman of the NDRC and the first U.S. Presidential Science Advisor systematically applying science to develop advanced weapons. The U.S., alone among all the Axis powers and Allied nations, now had a science advisor who reported directly to the president and had the charter and budget to fund advanced weapon systems research – outside the confines of the Army or Navy.

NRDC was run by science administrators, who had managed university researchers as well as complex research and applied engineering projects science before. They took input from theorists, experimental physicists, and industrial contractors, and were able to weigh the advice they were receiving. They understood the risks, scale and resources needed to turn blackboard theory to deployed weapons. Equally important, they weren’t afraid to make multiple bets on a promising technology nor were they afraid to kill projects that seemed like dead ends for the war effort.

200+ contracts
Prior to mid 1940 research in U.S. universities was funded by private foundations or companies. There was no government funding. The NRDC changed that. With a budget of $10,000,000 to fund research proposed by the five section chairmen, the NDRC funded 200+ contracts for research in radar, physics, optics, chemical engineering, and atomic fission.

For the first time ever, U.S. university researchers were receiving funding from the U.S. government. (It would never stop.)

The Uranium Committee
In addition to the five NRDC divisions working on conventional weapons, the NRDC took over the moribund standalone Uranium Committee and made it a scientific advisory board reporting directly to Bush. The goal was to understand whether the theory of an atomic weapon could be turned into a practical weapon. Now the NRDC could directly fund research scientists to investigate ways to separate for U-235 to make a bomb.

What Didn’t Work at the NRDC?
After a year, it was clear to Bush that while the NDRC was funding advanced research, the military wasn’t integrating those inventions into weapons. The NRDC had no authority to build and acquire weapons. Bush decided what he needed was a way to bypass traditional Army and Navy procurement processes and get those advanced weapons built. 

Read the sidebars for background.

The Office of Scientific Research and Development Stands Up
In May 1941 Bush went back to President Roosevelt, this time with a more audacious request: Turn NRDC into an organization that not only funded research but built prototypes of new advanced weapons and had the budget and authority to write contracts to industry to build these weapons at scale. In June 1941 Roosevelt agreed and signed the Executive Order creating the Office of Scientific Research and Development (OSRD).  (It’s worth reading the Executive Order here to see the extraordinary authority he gave OSRD.)

OSRD expanded the National Defense Research Committee’s (NDRC) original five divisions into 19 weapons divisions, five research committees and a medical portfolio. Each division managed a broad portfolio of projects from research to production, and deployment. Its organization chart is shown below.

These divisions spearheaded the development of an impressive array of advanced weapons including radar, rockets, sonar, the proximity fuse, Napalm, the Bazooka and new drugs such as penicillin and cures for malaria.

The OSRD was a radical experiment. Instead of the military controlling weapons development Bush was now running an organization where civilian scientists designed and built advanced weapons systems. Nearly 10,000 scientists and engineers received draft deferments to work in these labs.

As a harbinger of much bigger things, the NRDC uranium committee was enlarged and renamed the S-1 Section on Uranium.

Throughout the next year the pace of atomic research picked up. And Bush’s involvement in launching the U.S. nuclear weapons program would grow larger.

 By the middle of 1941 Bush was beginning to believe that building an atomic bomb was possible. But he felt he did not have enough evidence to suggest to the president that the country commit to the massive engineering effort to build the bomb.

Then the MAUD report from the British arrived.

The British Nuclear Weapons Program codenamed “Tube Alloys” and the MAUD Report

Meanwhile in the UK, British nuclear physicists had not only concluded that building an atomic bomb was feasible, but they had calculated the size of the industrial effort needed.In March 1940 scientists had told UK Prime Minister Winston Churchill that nuclear weapons could be built.

In June 1940 the UK formed the MAUD Committee to study the possibility of developing a nuclear weapon. A year later they had their answer: the July 1941 the MAUD Committee report, “Use of Uranium for a Bomb,” said that it was possible to build a bomb from uranium using gaseous diffusion on a massive scale to produce uranium-235. It kick-started the UK’s own nuclear weapons program called Tube Alloys. (Read the MAUD report here.)

They delivered their report to Vannevar Bush in July 1941. And it changed everything.

Bush is Convinced by the MAUD Report
The MAUD Report finally pushed Bush over the edge. The British report showed how it was possible to build an atomic bomb. The fact that the British were independently saying what passionate advocates like Lawrence, Fermi, et al were saying convinced Bush that an atomic bomb program was worth investing in at the scale needed.

For a short period of time in 1941 the UK was ahead of the U.S. in thinking about how to weaponize uranium, but British officials dithered on approaching the U.S. for a full nuclear partnership with the U.S. By mid 1942, when the British realized their industrial capacity was stretched too thin and they couldn’t build the uranium separation plants and Bomb alone during the War, the Manhattan Project was scaling up and the U.S. had no need for the UK.

The UK would play a minor role in the Manhattan project.

Bush Tells Roosevelt – We Can Build an Atomic Bomb
In October 1941, Bush told the President about the British MAUD report conclusions: the bomb’s uranium core might weigh twenty-five pounds, its explosive power might equal eighteen hundred tons of TNT, but to separate the U-235 they would need to build a massive industrial facility. The President asked Bush to work with the Army Corps of Engineers to figure out what type of plant to build, how to build it and how much would it cost.

A month later, in November 1941 the U.S. National Academy of Sciences confirmed to Bush that the British MAUD report conclusions were correct.

Bush now had all the pieces lined up to support an all-out effort to develop an atomic bomb.

December 1941 – Let’s Build an Atomic Bomb
In December 1941, the day before the Japanese attack on Pearl Harbor, the atomic bomb program was placed under Vannevar Bush. He renamed the Uranium program as the S-1 Committee of OSRD.

In addition to overseeing the 19 Divisions of OSRD, Bush’s new responsibility was to coordinate all the moving parts of the atomic bomb program – the research, the lab experiments, and now the beginning of construction contracts.

With the Presidents support, Bush reorganized the program to take it from research to a weapons program. The goal now was to find the best ways to produce uranium-235 and Plutonium in large quantities. He appointed Harold Urey at Columbia to lead the gaseous diffusion and centrifuge methods and heavy-water studies. Ernest Lawrence at Berkeley took electromagnetic and plutonium responsibilities, and Arthur Compton at Chicago ran chain reaction and weapons theory programs. This team proposed to begin building pilot plants for all five methods of separating U-235 before they were proven. Bush and Conant agreed and sent the plan to the President, Vice President, and Secretary of War, suggesting the Army Corps of Engineers build these plants.

With U.S. now at war with Germany and Japan, the race to build the bomb was on.

In January 1942, Compton made Oppenheimer responsible for fast neutron research at Berkeley. This very small part of the atomic bomb program is the first time Oppenheimer was formally engaged in atomic bomb work.

Enter the Army
The Army began attending OSRD S-1 (the Atomic Bomb group) meetings in March 1942. Bush told the President that by the summer of 1942 the Army should be authorized to build full-scale plants.

Build the U-235 Separation and Plutonium Plants
By May 1942 it was still unclear which U-235 separation method would work and what was the right way to build a nuclear reactor to make Plutonium, so the S-1 committee recommended – build all of them. Build centrifuge, electromagnetic separation, and gaseous diffusion plants as fast as possible; build a heavy water plant for the nuclear reactors as an alternative to graphite; build reactors to produce plutonium; and start planning for large-scale production and select the site(s).  The S-1 Committee also recommended the Army be in charge of building the plants.

Meanwhile that same month, Oppenheimer was made the “Coordinator of Rapid Rupture.” He headed up a group of theorists working with experimentalists to calculate how many pounds of U-235 and Plutonium were needed for a bomb.

The Manhattan Engineering District – The Atomic Program Moves to the Army
In June 1942, the president approved Bush’s plan to hand building the bomb over to the Army.  The Manhattan Engineering District became the new name for the U.S. atomic bomb program. General Groves was appointed its head in September 1942.

To everyone’s surprise Groves selected Oppenheimer to administer the program. It was a surprise because up until then Oppenheimer was a theoretical physicist, not an experimentalist nor had he ever run or managed any programs.

Grove and Oppenheimer decided that in addition to the massive production facilities – U-235 in Oak Ridge, TN, and Plutonium in Hanford, WA – they would need a central laboratory to design the bomb itself. This would become Los Alamos. And Oppenheimer would head that lab bringing together a diverse set of theorists, experimental physicists, explosive experts, chemistry, and metallurgists.

Bush, Conant and Grove at Plutonium production site at Hanford -July 1945

At its peak in mid-1944 130,000 people were working on the Manhattan Project; 5,000 of them worked at Los Alamos.

Vannevar Bush would be present at the test of the Plutonium weapon at the Trinity test site in July 1945.

The OSRD would be the organization that made the U.S. the leader in 20th century research. At the end of World War II, Bush laid out his vision for future U.S. support of research in an article called “Science the Endless Frontier.” OSRD was disbanded in 1947, but after a long debate it was resurrected in pieces. Out of it came the National Science Foundation, the National Institute of Health, the Atomic Energy Commission and ultimately NASA and DARPA – all would all spring from its roots.

50 years before it happened Bush would describe what would become the internet in a 1945 article called As We May Think.


  • By the time Oppenheimer and Grove took over the Atomic Bomb program, Vannevar Bush had been running it for two years
  • The U.S. atomic bomb program was the sum of multiple small decisions guided by OSRD and a Presidential science advisor – Vannevar Bush
  • Bush’s organizations kick-started the program. The NDRC invested (in 2023 dollars) $10M in nuclear research, OSRD put in another $250M for nuclear experiments
  • The Manhattan project would ultimately cost ~$40 billion to build the two bombs.
  • As the country was in a crisis – decisions were made in days/weeks by small groups with the authority to move with speed and urgency.
  • Large-scale federal funding for science research in U.S. universities started with the Office of Scientific Research and Development (OSRD) – more to come in subsequent posts
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