Acting on Fuch’s treachery and other intelligence, Stalin assembled his own team of physicists and other immensely talented scientists. Following the bombings of Hiroshima and Nagasaki, he called for an all-out crash program in atomic research and development. The first Soviet production reactor arrived in the fall of 1948.1

This intense research effort, likely carried out under penalty of death, culminated in the first Soviet atomic bomb test in August 1949. The world now had two nuclear powers. “Shortly after the US launched its hydrogen bomb program in the early 1950s, the USSR followed suit and initiated their own hydrogen bomb program.2

And so began both the nuclear arms race between the two superpowers and the realization by other nations that they needed either a bomb of their own or the reliable guarantee of someone with the bomb to assure their sovereignty if attacked by an atomic adversary - the “nuclear umbrella”. This was a rational approach to the new atomic world and by 2025 there were nine nations in the ‘nuclear club’.

Currently, there are estimated to be 9,585 nuclear warheads in military stockpiles for potential use across nine countries, with Russia and the U.S. accounting for 8,088 of these. There are also an estimated 2,536 retired warheads that are yet to be dismantled.3

Edward Teller was an integral part of the work at Los Alamos during the Manhattan Project. His main contribution was on the implosion method and supporting theoretical calculations necessary for the plutonium bomb used on Nagasaki. While both the uranium and plutonium bombs relied on nuclear fission to unleash their awesome power Teller became intrigued with the idea of using fusion instead of fission. He clung to this concept throughout the Manhattan Project.

Fusion is the process that fuels the sun. Instead of splitting heavy atoms it requires compressing light atoms to enormous pressures. To initiate meaningful amounts of fusion energy, The fuel must be actively heated to at least 100 million degrees (hotter than the sun) while confining it long enough (keeping the nuclei close enough together) to sustain fusion reactions.1 This became known as a thermonuclear bomb.

After the war ended Teller continued his advocacy and once the USSR successfully tested its first atomic bomb in 1949, he lobbied Truman to pursue “The Super”. The president authorized the project a year later with Teller at its scientific helm. The design was completed in 1951 with liquid deuterium as its fusion fuel and a large fission weapon (aka atomic bomb) as its trigger.2

The first test (Ivy Mike) was completed in 1952 on the island of Elugelab in Enewetak Atoll producing a blast of 10.4 megatons, almost 700 times the power of the Hiroshima bomb, and effectively erasing the island from the earth.. While the test was successful it only proved the concept as the entire structure was 20 feet high and weighed over 160000 lbs. including it’s refrigeration equipment.

Work began immediately to build a deliverable version of this new weapon. Once again, as in the Manhattan Project, the main lithium-6 fuel was not readily available and it took until 1954 to accumulate the required amount.3 The actual design of the bomb remains classified although virtually all current nuclear warheads are thermonuclear.

Image source: https://www.twz.com/nuclear/return-to-icbms-armed-with-multiple-warheads-suggested-by-stratcom-boss accessed August 4, 2025

The initial design for the uranium bomb (Little Boy) was based on a ‘gun’ design where a uranium projectile was fired into a uranium target achieving critical mass and a sustainable chain reaction.

By the time Little Boy was assembled, 50 kg of uranium was available at Oak Ridge, and an additional 14 kg of was on hand. All of it was used in the bomb. Although all 64 kg of the uranium was used, only 1.09 kg of the 64 kg of uranium in Little Boy underwent fission and became energy.

This inefficiency along with the difficult enrichment process to produce U235 led to the investigation of plutonium (discovered in 1940) as a substitute fissile material. The physicists involved concluded a new design, the implosion method was required. “In the implosion-type device, a core of sub-critical plutonium is surrounded by several thousand pounds of high-explosive designed in such a way that the explosive force of the HE is directed inwards thereby crushing the plutonium core into a super-critical state.”1

This focused explosion compresses the softball sized pit down to the size of a tennis ball. The design only required about 13.6 lbs of plutonium and while only 1 kilogram fissioned the blast yielded 21 kilotons (compared to 15 for Little Boy) and was considered 10 times as efficient as Little Boy.2 Once this design was proven by. the Trinity test all future manufacture of atomic weapons employed the plutonium implosion approach.

Interestingly, although Little Boy was used first, it was never tested. Components were individually tested, but the entire bomb was not. A test was impossible because it would have used all the enriched uranium available, leaving none left for the actual bomb to be used. In addition “ … confidence in the uranium-235 gun-type bomb design and the lack of extra fissile material for experimental trials, testing it before combat use was deemed unnecessary”.3

Upon Roosevelt’s authorization General Groves immediately went to work, securing uranium supplies and building infrastructure. The entire project spanned just 4 years (1942-1946) and achieved its objective of building and detonating the first atomic bomb in 1945. The project was remarkable for its size, organization and secrecy.

At its peak in 1944 129,000 people were employed, most at the three sites of Oak Ridge, TN, Hanford, WA and the smallest but most well known Los Alamos, NM. Approximately $2 billion in 1940s dollars was spent, equivalent to over $30 billion in 2023 dollars. All of this effort culminated in the production of just 3 atomic bombs. Two were used to bomb Hiroshima and Nagasaki forcing Japan’s surrender.

While a third core was built, it was eventually disassembled and repurposed. This core came to be known as the “Demon Core” after two fatal incidents when it was accidentally put into a critical configuration. Both scientists (Harry Daghalian 1945 and Louis Slotin 1946) died shortly after from acute radiation exposure. The core was eventually melted down and reused to build additional cores.

After the Japanese surrender the Manhattan project continued to produce bombs and slowly build the U.S. nuclear arsenal. After passage of the Atomic Energy Act in 1946 and “[by]y early 1947, the nation's atomic energy establishment amounted to little more than the remnants of the military organization and facilities that had produced the world's first atomic weapons. “1

In early 1940, the committee recommended “that the government fund limited research on isotope separation as well as Enrico Fermi’s and Leo Szilard’s work on fission chain reactions at Columbia University.”2 In other words, uranium was the focus - not necessarily an atomic bomb. This was prior to the discovery of plutonium in December 1940.

Early in 1939 Hitler had annexed the Sudetenland and later that year invaded Czechoslovakia. This was one of the three uranium production areas in the world, in addition to the Belgian Congo, Canada, and to a much smaller degree, Colorado. Hitler’s control of Czech uranium was a major concern of the U.S., although the Germans did not actively pursue an atomic bomb until 1942 3

The Shinkolobwe mine in the Katanga province of the Belgian Congo, in addition to not being controlled by Hitler, was also home to the richest uranium ore in the world. Shinkolobwe provided two-thirds of the Manhattan Project's uranium from an extraordinarily rich pitchblende deposit averaging more than 2 percent uranium content. Virtually all of this had been mined and was above ground at the start of the war. 4

In June of 1941 the president blended the initial uranium committee into a new committee, the National Defense Research Council (NDRC). The committee chair banned all foreign born scientists from committee membership. The section on uranium was renamed S-1.

In July 1941, a London group codenamed MAUD Committee produced a report estimating that “… a critical mass of ten kilograms [of uranium 235] would be large enough to produce an enormous explosion.”5 This report was shared with the NDRC. Subsequent discussions pertaining to its contents are likely the first point at which Soviet intelligence learned of the atomic bomb project.6 In October 1941, NDRC Chairman Vannevar Bush briefed the president and vice president on the report. “Roosevelt instructed him to move as quickly as possible but not to go beyond research and development. Bush, then, was to find out if a bomb could be built and at what cost but not to proceed to the production stage without further presidential authorization.”7

“In accordance with the instructions he received from Roosevelt, Bush removed all uranium work from the National Defense Research Committee. From this point forward, broad policy decisions relating to uranium were primarily the responsibility of the Top Policy Group, composed of Bush, James Conant, Vice President Wallace, Secretary of War Henry L. Stimson, and Army Chief of Staff George C. Marshall.”8

In early 1942 Japan had achieved several military victories in the Pacific - increasing the urgency for the U.S. to develop some sort of advantage. In August the Army Corps of Engineers established the Manhattan Project to manage the research necessary to separate U235 from U238 as well as atomic bomb design and research, appointing Brigadier General Leslie Groves as its leader. That December FDR gave his final authorization to proceed with building an atomic bomb.9

As physicist explored and advanced the field of nuclear theory in the early 1900s extraordinary insights were gained. Marie Curie’s investigations into radioactivity (a term coined by her, designating a new form of energy) made her the first woman to win the Nobel prize in 1903 and her later work in 1911, made her the first person to win it twice.

She and her husband Pierre’s experiments showed that the atom was NOT the smallest constituent of matter but could emit even smaller particles. Thus the field of particle physics was born.

Her relentless research led to her death by radioactive poisoning. Her was body so radioactive a lead-lined coffin was needed to bury her. To this day her notebooks are so radioactive that they are stored in lead-lined boxes. Visitors inspecting these documents must don protective clothing and sign liability waivers.

If you want to see those notebooks in street clothes, you’ll need to wait a long time as the most common isotope of radium, radium-226, has a half life of 1,601 years.

Curie’s discovery led to a flurry of experimentation in the physics and chemistry communities. This included Frederic and Irene (nee Curie) Joliot’s discovery of artificial radiation in 1934. Working from that information Enrico Fermi in 1934 showed that by bombarding uranium nuclei with neutrons, 20 new radioactive substances were formed - all unexplained. Curie’s daughter Irene and later, independently in 1938, Otto Hahn proved the chemical behavior of these unexplained substances was identical to non-radioactive elements. Shortly after Hahn published his results, in 1939 Otto Frisch provided evidence that the actual nucleus of the uranium atom was broken up by this method. This was fission.

At breakneck speed, a month later in France Hans Halban and Lew Kowarski discovered a hugely important detail - during fission of a uranium atom secondary neutrons are released. This was a critical discovery because it revealed the possibility of a fission chain reaction. Up to this point all nuclei bombardment was done with an external source of neutrons.

Starting in the spring of 1939, with Hitler’s ambitions for world domination being unmasked not to mention unopposed, various scientists began to warn their governments of the importance of uranium and the need for resources to pursue atomic resource - atomic energy. Hungarian physicist Leo Szilard, who together with Edward Teller and Einstein eventually drafted the letter to Roosevelt, became obsessed with the idea of a nuclear weapon. He saw it as inevitable. and sent letters to his colleagues living in various (soon to be known as Allied) countries suggesting that they stop publication of all material dealing with nuclear fission.

This was a revolutionary concept in nuclear physics which previously had been thought of as ‘pure science’. Exchange of information was entirely unrestricted and at times had the nature of a race to push the frontiers. His proposal was not fully accepted but did result in each country soon treating uranium research results as secret.

In the summer of 1939 Frederic Joliot with Francis Perrin described the concept of critical mass. This was the required amount of uranium needed to sustain a chain reaction. The result were the first ever patents, filed in 1939 France, for applications of uranium chain reactions. One was for a uranium explosive and another for uranium based power production (a nuclear pile).

Hitler made his move into Poland in September of 1939, effectively unleashing the second World War. This spurred intensive research on the development of atomic weapons but at this point nobody had ever built one - or designed one. It was just a concept, a thought experiment.1

Roosevelt replied to Einstein’s letter2 10 weeks later in October 1939 informing him that he had established a commission (military and civilian) to study uranium.

In 1905 Albert Einstein published his famous relativity equation. We’ve all seen it since grade school. I’ve since learned this not simply some revered algebra formula, but that it describes the transformation of energy into matter and vice versa. I did say I was a layman! In other words, it’s a conversion formula – matter to energy.

Once I saw that dynamic, I began to grasp how much energy there is out there. Doesn’t matter the substance, the energy is the same. A gram of sugar has just as much energy as a gram of nails or a gram of snow, wood, steel … anything. And that energy is enormous. Now don’t be frightened as we stick our toe in a bit of math.

The reason the equation is a conversion formula is that c-squared constant. It means the speed of light squared. That’s a HUGE number. The speed of light is 300,000 kilometers per second (186,000 miles). Squaring that 300k number equals 90 billion. So, 1 kilogram of anything i.e. everything, contains 90 billion joules of energy(the unit of energy). Most people are more familiar with watts than joules, so think of a joule as how much energy it takes to expend 1 watt per second. For example, a 100-watt bulb would convert 100 joules of energy per second.

Relax, the math is almost over. I’m going through this exercise to impress upon you just how much energy there is all around us, indeed in us. So, getting back to our 90 billion joules of energy baseline from 1 kilogram of matter, that is also equal to 21,000 tons of TNT exploding. The Hiroshima atom bomb was only 15,000 tons equivalent. I’ll come back to this huge multiplier later.

Rutherford’s discovery that (virtually) all the mass of an atom lies in its nucleus, coupled with Einstein’s formula means there are huge amounts of energy in every atom around us. Harnessing that energy could unleash fearsome force.

Mass transforms to energy in many ways. A struck match releases, heat, light, smoke, ash, odors – all forms of energy released by the lighting. The key to the harnessing statement above is releasing and dictating the form of the energy released. This quest occupied many physicists’ experimentation in the 1930s and 40s.

So I start with my first question triggered by a copy of Richard Rhode’s superb book “The Making of the Atomic Bomb” on a shelf. We pretty much all know the outlines of the Manhattan Project, but I wondered “If you were writing a history of the atom bomb, where would you start?”.

It turns out we start with Earnest Rutherford’s 1911 experiments which yielded the new nuclear model of the atom. At the time common theory held an atom contained negatively charged particles called electrons imbedded evenly in some positively charged environment. This was the ‘plum pudding’ theory.

Rutherford’s experiments revealed that the nucleus was instead a tiny, dense positively charged composite unit at the center of an atom; itself containing protons and neutrons, constituting nearly the entire mass of the atom.

The previously accepted ‘plum pudding’ atomic model held that an atom’s mass and charge were uniformly distributed throughout the atom. So Rutherford’s advance was understanding the atom had a tiny, dense ‘nucleus’ surrounded by electrons.

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