NUCLEAR WEAPONS.

On the morning of 6 August 1945, an American bomber dropped "Little Boy" on the Japanese city of Hiroshima, killing tens of thousands of people and demonstrating to the world the awesome power of a new kind of weapon. Little Boy was an atomic bomb, the product of a secret U.S.-British-Canadian wartime effort known as the Manhattan Project. Over the years that followed, nuclear weapons transformed thinking about war and international politics. They were one of the central facts of the Cold War (1945–1989), shaping the conflict between the superpowers and sparking major crises. Their incredible destructive power threatened to destroy humanity but, simultaneously, formed the basis of international stability and peace.

ORIGINS AND THE MANHATTAN PROJECT

The roots of the Manhattan Project lay in the scientific achievements of the interwar period. In 1932 John Douglas Cockcroft (1897–1967) and Ernest Thompson Sinton Walton (1903–1995) of Cambridge University split an atom of lithium, proving that an atom's nucleus could be broken apart, releasing energy in the process. Building on Cockroft and Walton's work, the Italian physicist Enrico Fermi (1901–1954) showed that the atoms of almost every element could be split via neutron bombardment. This discovery, for which he won the Nobel Prize in 1938, raised the possibility of large-scale nuclear fission. According to this idea, one could start a chain reaction by splitting a few atoms of a radioactive substance (such as uranium), which would release both energy and neutrons, which in turn would split surrounding atoms, releasing still more energy and more neutrons. The result would be a huge amount of energy. Like many other European physicists in the 1930s, Fermi emigrated to the United States in order to escape the rising tide of fascism and anti-Semitism in Europe. Arriving in New York in 1939, and then moving to the University of Chicago, he produced the first controlled nuclear chain reaction in late 1942. The achievement was of major significance to the Manhattan Project, then already under way for more than a year.

In the late 1930s, a number of European émigré scientists worried that the Germans were trying to build an atomic bomb. If this happened, the consequences would be dire. On the basis of these concerns, Albert Einstein (1879–1955)—himself a German-Jewish refugee—wrote to President Franklin Delano Roosevelt (1882–1945) in August 1939, urging him to establish a program to accelerate the research already being done in American universities. Roosevelt agreed. The American government began to award grants for work on nuclear fission. The experiments that resulted formed the core of what became the Manhattan Project, which the president formally established in October 1941 by authorizing the development of atomic weapons.

Although Army General Leslie Richard Groves (1896–1970) was put in charge of the project, the American physicist Julius Robert Oppenheimer (1904–1967) was responsible for its scientific work. Oppenheimer established the project's headquarters at Los Alamos, New Mexico, and assembled a group of top scientists—many of whom had fled Europe—to collaborate on the research. Among those who worked on the project were Fermi, the German Hans Albrecht Bethe (1906–2005), the Hungarian Edward Teller (1908–2003), and the Austrian Victor Weisskopf (1908–2002), all leading experts on nuclear physics. One of the key problems facing the team was how to produce enough uranium-235, the element's fissionable isotope, and plutonium to build a bomb. To accomplish this task, enormous factories were built in Oak Ridge, Tennessee, and Richland, Washington, to extract uranium-235 from uranium ore and produce plutonium by bombarding uranium-238 with protons.

Once Fermi had established that a self-sustaining nuclear chain reaction was in fact possible, the only major obstacle left was how to turn the fissile material into a useful weapon. Two different kinds of bombs were built, one using uranium-235 and the other plutonium. In July 1945, two months after the German surrender, the first test of an atomic bomb took place in the New Mexican desert. Codenamed "Trinity," it produced an even bigger explosion than predicted. Less than a month later, the first atomic weapons used in war were dropped on Hiroshima and Nagasaki.

THE SOVIET BOMB

The American monopoly lasted scarcely four years. Even though the Soviets had been wartime allies, and even though the British and Canadians had been both allies and close collaborators on the Manhattan Project, the U.S. government asserted strict unilateral control over the manufacture of nuclear weapons after the war. Prior to 1945, there had been good reasons not to share any information with the Soviets. Though a partner in the fight against Nazi Germany, the Soviet Union had had an antagonistic relationship with the United States and Western Europe during the interwar period. During the war itself, it was doubtful whether the Soviets would withstand the German invasion. In these circumstances, it would have been foolish to share sensitive information with Moscow, because it could easily have ended up in Nazi hands. After the war, rising U.S.-Soviet tensions gave Washington cause to reconsider any thought of divulging its atomic secrets.

The Soviets made every effort to steal the Manhattan Project's secrets. Thanks to both the high quality of their espionage and sympathy for their cause among certain Western scientists, they were startlingly successful. Their most valuable spy in Los Alamos was Klaus Emil Julius Fuchs (1911–1988), a German-born physicist, devout communist, and longtime Soviet informer. So successful was he that none of his colleagues were aware of his covert activities. His work for Moscow was not discovered until 1950.

The information that he and others passed to the Soviets was of great use in both strategic and scientific terms. At the 1945 Potsdam Conference, the U.S. president Harry S. Truman (1884–1972) informed the Soviet leader Joseph Stalin (1879–1953) that the United States had built a "powerful new weapon." Long aware of the Manhattan Project thanks to the steady stream of information from Los Alamos, the Soviet leader feigned indifference, but was secretly concerned. There is some debate concerning whether Truman attempted—in what is called "atomic diplomacy"—to use the American nuclear monopoly to cow Stalin into concessions regarding eastern Europe. Regardless of whether this was Truman's intention, the Soviets certainly believed that the Americans were trying to frighten them, and they were determined to resist. Rejecting the Baruch Plan, an American proposal to bring atomic weapons under international control, Stalin ordered his scientists to build their own bomb as quickly as possible, and gave them all the resources and intellectual freedom necessary to do so.

They succeeded within four years. In August 1949 the Soviet Union conducted its first nuclear test. The intelligence that the Soviet spies had gathered certainly accelerated the development of the Soviet bomb, but it was by no means essential. The scientists working on the project, led by the physicist Igor Kurchatov (1903–1960) and overseen by Lavrenty Beria (1899–1953), the former head of the NKVD (People's Commissariat of Internal Affairs), were among the world's best and, in all likelihood, they would eventually have succeeded in building the bomb on their own. The infiltration of the Manhattan Project, as dramatic as it was, only saved the Soviets a few years of work. Nevertheless, the 1949 test was a huge surprise to the United States, which had expected to enjoy its monopoly until at least the early 1950s.

THE HYDROGEN BOMB

President Truman responded by ordering the construction of a hydrogen bomb, a fusion weapon that would be several hundred times more powerful than the fission bombs dropped on Japan. The decision was a controversial one among American scientists, many of whom, including Oppenheimer, opposed any further research on such devastating weapons. A hydrogen bomb would be so powerful, they argued, that it could only be used against civilian populations and was therefore inherently a tool of genocide. However, a number of equally eminent scientists supported Truman, including Edward Teller. Teller insisted that the Soviets would build a fusion bomb regardless of what the Americans did. The United States could not afford to be intimidated by the Soviet Union, leaving it no choice but to build a bomb of its own. Along with the hydrogen bomb came the counterintuitive idea that the weapon could be the cornerstone of international peace. If each side could threaten the other with total destruction, then neither would be willing to risk all-out war. This was the kernel of nuclear deterrence, the principle at the heart of Western and Soviet strategy for the duration of the Cold War.

By the time Truman approved the project in January 1950, the Soviets had already made good progress toward their own hydrogen bomb. Unlike their atomic bomb, which was largely based on American plans, Soviet scientists designed this weapon without outside help. Working under the guidance of the brilliant and young Andrei Sakharov (1921–1989), they scored a notable victory, detonating a deliverable bomb in August 1953, more than two years before the Americans. It is noteworthy that the Soviet government never wrestled with the same moral concerns about the hydrogen bomb that the Americans did, because from Moscow's point of view there was little qualitative difference between fission and fusion weapons. The American hydrogen bomb team, with Teller at its head, had tested a hydrogen device ahead of the Soviets, in November 1952 at Eniwetok Atoll in the Pacific. However, this device was so large and unwieldy—weighing more than eighty tons and requiring an enormous refrigerator—that it was of no military use. The test proved that it was possible to build a fusion device, but it took another three years for the Americans to build a usable bomb.

BRITISH AND FRENCH NUCLEAR WEAPONS

By the early 1950s, major changes in both American and Soviet strategy were under way. Nuclear and thermonuclear weapons were so powerful that it was difficult to consider their use in anything but all-out war. But in order to deter one's opponents from even low-level aggression, it was essential to convince them that one was willing to respond with all one's might. This logic undergirded President Dwight Eisenhower's (1890–1969) doctrine of massive retaliation, announced in 1954. One of the key problems with the strategy, however, was persuading American allies of its wisdom.

Right from the end of the Second World War, the United States refused to share either its nuclear research or the weapons themselves with its NATO (North Atlantic Treaty Organization) allies. Washington had pledged to defend these countries against Soviet attack, but insisted on retaining the final say over if and when nuclear weapons would be used. The Western Europeans grew increasingly uncomfortable with this arrangement and disliked their outright reliance on a potentially unreliable ally on such a fundamental issue as national defense. As a result, the British and French insisted on developing their own independent nuclear deterrents.

British scientists had played a major role in the Manhattan Project but lacked access to crucial parts of the bombs' design. More work was needed. There was little debate within the new Labour government of Clement Richard Attlee (1883–1967) about whether it was worthwhile. Foreign Secretary Ernest Bevin (1881–1951), an adamant anticommunist, insisted that, as a great power with a large empire to govern, Britain needed its own nuclear arsenal. However, there was more to the question than just prestige. Wartime bombardment proved how vulnerable the country was to aerial attack, and nuclear weapons were the best way to deter any potential Soviet aggression. For these reasons, in January 1947 the government approved plans to build the bomb. In October 1952, shortly before the Americans tested their first hydrogen device, the British detonated an atomic bomb off the coast of Western Australia.

It took France rather longer to build an A-bomb. In the immediate aftermath of the Second World War, Charles de Gaulle (1890–1970) believed the country needed its own nuclear weapons, but France had fallen so far behind its allies in science and industry during the Nazi occupation that huge obstacles lay in its path. Strong domestic opposition from the Left meant that there was little political will behind the idea. However, after the 1954 defeat at Dien Bien Phu, the French government was determined to rebuild national prestige. The design and production of nuclear weapons was one way to achieve this goal, and the government of Pierre Mendès-France (1907–1982) approved the project. When de Gaulle returned to power in 1958, he gave the idea his full support. France conducted its first successful test in February 1960.

The logic behind the independent French nuclear arsenal, known as the force de frappe, was clear. De Gaulle was adamant that France had to remain a great power. In this light, it was unacceptable to rely on a foreign country—in this case, the United States—on a matter that went to the very heart of national pride. He also shared many of London's fears about the American commitment to his country's defense and believed that, for reasons of both security and prestige, France needed to maintain a certain distance from the United States and NATO on military matters. There was no way to guarantee Washington's full support in the event of Soviet aggression, so France had to be ready to defend itself. Although these were reasonable concerns in theory, they did not hold up well in practice. The force de frappe came into being, but it was an open secret that it would never have been possible without a significant amount of American support. Just as Britain had to abandon its independent nuclear program in 1960 in order to cut costs, France still had to rely on the United States.

MUTUALLY ASSURED DESTRUCTION AND THE CUBAN MISSILE CRISIS

In nuclear weapons' first decade, they existed only in the form of bombs to be dropped from the air. The advances of the 1950s brought new ways to wage nuclear war. Alongside its nuclear research, the Soviet Union had been working on rocket technology with a view to building rockets that could be sent into space. It reached its target in 1957, when it launched a small satellite named Sputnik into orbit. Sputnik itself was not of great strategic value, but the rocket that propelled it was. If the Soviets could send a rocket into space, it followed that they could also hit any point in the world with that same rocket. They now had the ability to strike in the United States with a nuclear-armed missile.

The advent of Inter-Continental Ballistic Missiles (ICBMs) changed the Cold War's nuclear calculus. Prior to 1957, much of the continental United States was safe from atomic attack because it was out of range of even the best Soviet bombers. Sputnik destroyed this immunity. The result was panic in both the United States and Western Europe, and the start of a crash program to develop American missiles. A year later—with the help of German scientists such as Wernher von Braun (1912–1977), who had previously worked for the Nazis—the Americans succeeded, sending their own satellite into orbit. Nevertheless, there were widespread fears in Washington of a "missile gap" between the United States and the USSR, spurred on by the characteristically folksy boast of Nikita Khrushchev (1894–1971) that his country was producing missiles as quickly as it did sausages. Through U-2 surveillance flights over the Soviet Union, the Americans soon learned that the advantage in missile production was in fact theirs.

Regardless, the combination of ICBMs and hydrogen bombs meant that the stakes of the nuclear standoff were as high as they could possibly be. Before the development of the H-bomb, there remained the possibility that nuclear war, however horrible, could remain limited. Now, however, a full-scale war waged with thermonuclear missiles would almost certainly destroy entire countries and might even make the planet uninhabitable. On this basis arose the principle of mutually assured destruction, appropriately known as MAD. Neither the United States nor the USSR stood a chance of surviving, let alone winning, a nuclear war. In theory, this certainty would guarantee peace, because neither side could afford even the smallest risk of hostilities.

The theory came under severe strain during the Cuban missile crisis. The crisis was the single most dangerous moment of the Cold War and proved the risks of the nuclear arms race to both superpowers. The Soviet Union began sending nuclear missiles to Cuba after the Bay of Pigs, a failed American attempt in 1961 to overthrow the island's new socialist leader, Fidel Castro (b. 1926). Khrushchev was eager to support the young Cuban leaders, who reminded him of his own revolutionary past. Moreover, Cuba was an ideal site for the USSR's intermediate-range missiles and a beachhead for spreading communism to Latin America. Khrushchev believed he had the perfect opportunity to retaliate against the recent deployment of intermediate-range American missiles in Turkey and to restore some semblance of a strategic balance between East and West, especially given the USSR's relative lack of ICBMs.

When a U-2 flight discovered the Cuban missiles in October 1962, the American government faced a crisis. It could not tolerate hostile nuclear missiles so close to home, but how could it remove them? The administration of John Fitzgerald Kennedy (1917–1963) considered a number of options, including a full-scale invasion of Cuba, air strikes against the launch sites, and a naval blockade to prevent further missile shipments from getting through. The slightest provocation could trigger a nuclear attack on the United States, which would spark full retaliation and end only in mutual annihilation. Kennedy opted for the blockade. The first Soviet ship to encounter the blockade turned around, opening the door to a settlement. After secret negotiations, Khrushchev agreed to pull the missiles out of Cuba if the United States would remove its missiles from Turkey. Kennedy agreed, and the crisis came to an end.

ARMS CONTROL EFFORTS

The Cuban missile crisis was the clearest indication yet of how easy it would be to tumble into a catastrophic nuclear war. Some kind of arms control was necessary to reduce this danger. The first step in this direction came the year after the crisis, with the signing of the Limited Test Ban Treaty (LTBT). According to its provisions, signatories pledged to stop atmospheric tests of nuclear weapons in order to restrict their development and end the provocations that typically followed each test. All future tests had to happen underground.

The agreement was a modest but signal step, the first attempt to contain the use of nuclear weapons. In August 1963, the Americans, Soviets, and British signed the treaty. Insisting as ever on its independence, the only other nuclear power, France, refused to join them. Two months later, the superpowers also agreed to ban nuclear weapons from space.

Further progress was made in the late 1960s and into the 1970s, an era of calm and stability compared with the early Cold War years. Following the LTBT, the next major milestone was the Nonproliferation Treaty (NPT), concluded in 1968. Despite another French refusal to participate, the Americans, Soviets, and British brought the negotiations to a successful conclusion. The treaty committed them to prevent the spread of nuclear weapons to other countries. The higher the number of states that had nuclear weapons, the reasoning went, the greater the danger of their use in a conflict. Prestige was also on the line, since if the nuclear club could be kept small, the value of membership would remain commensurately high. Indeed, the three signatories gave no serious thought to reducing their stockpiles. It was enough to prevent others from building their own.

Into the 1970s, the superpowers refused to cut back the numbers of their missiles and weapons. They instead agreed to restrict their growth. SALT—the Strategic Arms Limitation Talks—was the result. Starry-eyed idealism motivated neither superpower. Each had pragmatic goals: the Russians some relief from the arms race at a time of economic trouble and the Americans a strategic advantage and fodder for President Richard Nixon's (1913–1994) reelection campaign. Negotiated both by arms control experts in Helsinki and Vienna and between the U.S. national security advisor Henry Kissinger (b. 1923) and the Soviet ambassador Anatoly Dobrynin—the so-called backchannel—the SALT agreements placed limits on antiballistic missile defenses and froze the construction of missile launchers for five years. These results were not overwhelming, but both sides were optimistic that they had built a solid foundation for future progress.

Nixon's successor, Gerald Ford (b. 1913), attempted to maintain the momentum that SALT had generated. In 1974 he and Leonid Brezhnev (1906–1982) agreed on a set of guidelines for the next round of arms control talks, known as SALT II. The goal was to pick up where the first agreement had left off, but the United States refused to discuss its nuclear forces in Europe, a key area of interest for the Soviets. Brezhnev, determined not to let the talks collapse, pressured his domestic critics—especially within the military—to accept the American terms. He succeeded, and negotiators agreed to a maximum of 2,250 missile launchers each. But Ford's successor, Jimmy Carter (b. 1924), insisted on cuts that were even more radical and less acceptable to the skeptics within the Soviet government. Brezhnev and the Soviet military were furious. It took until 1979 to repair the damage and reach a new agreement.

Although a deal was reached, it was never implemented. The United States Senate insisted that the agreement was unverifiable because there was no way to ensure that the Soviets would hold up their end of the bargain. Moreover, the broader process of détente collapsed in the wake of the Soviet invasion of Afghanistan in 1979 and the election of Ronald Reagan (1911–2004) in 1980. Hopes for arms control fell apart as Cold War tensions returned to levels unseen since the early 1960s.

ABLE ARCHER, GORBACHEV, AND THE END OF THE COLD WAR

Reagan came into office on a strong anticommunist platform. Rejecting any further arms control talks, he massively increased the American military budget. Part of this renewed toughness was the deployment of new nuclear missiles—Cruise and Pershing 2—in Western Europe as a response to the Soviets' recent installation of the new SS-20 missiles. Protestors organized massive rallies to oppose the move, but failed to stop it.

In this context of heightened tension, NATO staged a war game, dubbed "Able Archer," in late 1983. The Soviet military detected the exercises but, already on edge because of Reagan's bellicose rhetoric, mistook them for the prelude to a Western attack. Moscow put its forces on alert, ready to respond with nuclear weapons if necessary. The danger was not as acute as it had been during the Cuban missile crises, but both sides still approached the brink of nuclear war without ever intending to. The episode reminded Washington and Moscow of the wisdom of returning to the negotiating table.

The rise to power in 1985 of Mikhail Gorbachev (b. 1931) provided the opportunity for new arms control talks. In 1986 Gorbachev publicly proposed a plan to eliminate all nuclear weapons by the year 2000. The proposal was bold and unprecedented, and it caught the Reagan administration's attention. When the two leaders met at Reykjavik later that year, Gorbachev renewed his offer, and Reagan responded enthusiastically. However, the Soviet leader insisted that the Americans would have to abandon their Strategic Defense Initiative—a research program, popularly known as "star wars," to build a shield against ballistic missiles—before any deal could be reached. Reagan refused. The summit ended without agreement.

This was only a temporary setback. Both sides were now considering massive cuts to their nuclear arsenals, a situation that could not even have been contemplated five years earlier. They renewed their efforts, and reached a deal at the Washington summit in December 1987, agreeing to eliminate their nuclear weapons stationed in Europe. The Intermediate-Range Nuclear Forces (INF) treaty came into force in June 1988. This was the beginning of the end of the nuclear standoff that had lasted almost forty years.

The next major milestone came after the fall of the Berlin Wall in 1989. In July 1991 the United States and the USSR signed the Strategic Arms Reduction Treaty (START), the culmination of negotiations that had begun while Reagan was still in office. The first major commitment to reduce nuclear stockpiles since the invention of the atomic bomb, it required both sides to cut their arsenals by almost a third. It was a major accomplishment and proof that the Cold War was effectively over. The USSR itself collapsed in December, devolving the treaty's obligations onto its successor states. President George Herbert Walker Bush (b. 1924) and his Russian counterpart Boris Yeltsin (b. 1931) signed START II in January 1993. The treaty expanded on START I, radically restricting the possession of nuclear weapons and delivery systems to between three thousand and thirty-five hundred on each side. After ratification by the U.S. Senate in 1996 and the Russian Duma in 2000, it was superseded by the 2002 Strategic Offensive Reduction Treaty (SORT), which capped each side's nuclear arsenal between seventeen hundred and twenty-two hundred warheads.

Nuclear weapons continue to be a major issue in international politics, but the focus has shifted away from the major powers. There is increasing concern, particularly in the West, about the proliferation of nuclear weapons both to smaller states and to nonstate actors, especially terrorist networks. The Indian subcontinent has been relatively stable since the surprise Indian and Pakistani nuclear tests of 1998, but in the early twenty-first century there have been worries that North Korea and Iran were developing weapons of their own. In a similar vein, the American government cited Iraq's alleged nuclear weapons as a justification for the invasion of that country in 2003. Given the number of weapons in existence worldwide—and the availability of so-called suitcase bombs—it is impossible to stop the spread of nuclear technology completely. The threat of nuclear proliferation is one of the severest tests facing the international system in the early twenty-first century. Deterrence provided the basis for stability during the Cold War, but it remains to be seen whether any similar idea can be found to avert the use of nuclear weapons in years to come.

See alsoCold War; Cuban Missile Crisis; Disarmament; Potsdam Conference.

BIBLIOGRAPHY

Beach, Sir Hugh, and Nadine Gurr. Flattering the Passions; or, The Bomb and Britain's Bid for a World Role. London, 1999.

Carlisle, Rodney, ed. Encyclopedia of the Atomic Age. New York, 2001.

Craig, Campbell. Destroying the Village: Eisenhower and Thermonuclear War. New York, 1998.

Fursenko, Aleksandr, and Timothy Naftali. One Hell of a Gamble: Khrushchev, Castro, and Kennedy, 1958–1964. New York, 1997.

Holloway, David. Stalin and the Bomb: The Soviet Union and Atomic Energy, 1939–1956. New Haven, Conn., 1994.

Rhodes, Richard. The Making of the Atomic Bomb. New York, 1986.

Michael D. J. Morgan