How the Nuclear Arms Race Works

­The U.S. was equally conflicted about sharing atomic information with the Soviet Union. Many scientists, including Niels Bohr and Robert Oppenheimer, felt it best to allow a "free interchange of information" of atomic knowledge. Enough was known in the world of physics for the Russians to build a bomb eventually, with or without help from America.

Also, withholding information might upset political ties between the two countries, both of which were coming out of World War II as major superpowers. On the other hand, a growing distrust of communism had already formed within many Americans by the end of the war, so some wanted to keep nuclear secrets out of Soviet hands. An American monopoly on nuclear weapons would make Russia more manageable from a political standpoint.

It was this kind of tension that sparked a nuclear arms race, a frantic era in which several nations tested nuclear technology and stockpiled thousands of nuclear warheads in an effort to get ahead of one another. Like the space race, whoever had the best technology had the most power, but this was a much more dangerous game — the potential of an all-out nuclear war between nations always loomed, and the 20th century is littered with uneasy international policies and near catastrophes.

To learn about the nuclear arms race and the people and organizations involved with it, read on.

I­n the aftermath of Hiroshima and Nagasaki, the United Nations established the Atomic Energy Commission (AEC) in an attempt to disarm any and all nuclear weapons and establish international control on atomic information. An initial plan from the United States, informally titled the Acheson-Lilienthal Report, suggested an international "Atomic Development Authority" that would control a monopoly on weapons and information. A subsequent revision of the report called the Baruch Plan (named after its author, Bernard Baruch) was nearly the same, except it included harsh penalties for nations who violated the plan's rules.

The Soviets rejected the plan outright, arguing that the U.S. was too far ahead in weapons development and would remain so until more details for international control were worked out. Americans, according to the Soviets, would use this lead to their advantage. Russia instead suggested the complete disarmament of nuclear weapons.

Any hope of agreement was lost — Soviet-American relations were already in sharp decline by 1946. Diplomat George Kennan sent the U.S. State Department an unusually long telegram in February that explained a distressingly hostile policy towards America (you can read all five parts of the message here).

Winston Churchill warned against communism in his famous "Iron Curtain" speech on March 5, claiming that the Soviets desired "the fruits of war and the indefinite expansion of their power and doctrines." Given that the Baruch Plan wasn't delivered until June of that year, a breakdown in relations between the two nations was well underway.

Soon after efforts over nuclear control crumbled, the U.S. went right back to business with testing nuclear bombs. In July, the military invited a large gathering of press members, congressmen and military officers to demonstrate a nuclear bomb's effect on large fleets of Navy ships. These tests, under the name "Operation Crossroads," were airborne and underwater attempts at Bikini Atoll in the Marshall Islands, located in the Pacific Ocean.

The first test on July 1, called Shot ABLE, performed as well as the Trinity and Nagasaki bombs, but a missed target made it less impressive. The second test on July 25, Shot BAKER, surpassed expectations. The blast destroyed or damaged 74 empty ships, shooting thousands of tons of water into the air. Worse, dangerous levels of radiation spread around the area, canceling a third test. The display succeeded in demonstrating the power of the bomb to a much wider audience.

The Soviets, meanwhile, had known about the U.S. bomb project for a long time. German-born physicist Klaus Fuchs was among the British scientists working at Los Alamos during the Manhattan Project. Although officials didn't find out for a few years, Fuchs had been passing information about nuclear bombs to the Soviet Union since 1945. By August 1949, the Soviets detonated their own atomic bomb, nicknamed "Joe-1" by Americans after Russian leader Joseph Stalin, in Kazakhstan.

To learn about the scramble for more bombs — and more powerful bombs — read on.

With the Soviets successfully testing their own nuclear weapons, the race was officially on. Little more than a month after the "Joe-1" test, the United States began expanding its production of uranium and plutonium. By the start of 1950, President Harry S. Truman announced the U.S. would continue research and development on "all forms of atomic weapons."

This "all forms" part was important. Initially, scientists working on the Manhattan Project considered two possible designs for an atomic bomb. They eventually chose to create a fission bomb, in which neutrons fired toward the nuclei of uranium or plutonium set off a massive chain reaction. This type of bomb was used on Hiroshima, Nagasaki and Bikini Atoll.

Edward Teller, a physicist at Los Alamos, suggested a thermonuclear fusion bomb — or hydrogen bomb. A fusion bomb operates by forcing together deuterium and tritium, two light isotopes of hydrogen. The resulting explosion would be theoretically many times more than that of a fission device, and almost without limit. Time didn't permit the completion of a fusion bomb, but Teller pushed for a chance to complete the device in order to keep one step ahead of the Russians.

On Nov. 1, 1952, the U.S. detonated the world's first hydrogen bomb, code-named "Ivy Mike," on the Enewetak Atoll of the Marshall Islands. The resulting explosion was about the same as 10 million tons of TNT or 700 times greater than the fission bomb dropped on Hiroshima. The cloud produced by the explosion was 25 miles high and 100 miles wide, and the island on which it exploded simply disappeared, leaving nothing but a gaping crater.

Again, Klaus Fuchs had delivered early information on the hydrogen bomb designs along with the fission bomb information, and by late 1955 the Soviets tested their own design.

One of the more distressing events of the 1950s was another Soviet development — the launch of Sputnik 1 on Oct. 4, 1957. The satellite was the first object to be launched into space by an intercontinental ballistic missile (ICBM), and the achievement caused a great scare in the U.S. If the Soviets could put a satellite into space, they could do the same thing with a nuclear warhead. Now, instead of having sufficient warning time for a nuclear attack by monitoring incoming airplanes, a missile could hit a target in less than an hour.

The 1950s also included the expansion of the nuclear club — the group of nations with tested nuclear weapons. England had worked together with the U.S. on the nuclear bomb design but because of limited funds during the war, their contributions were mainly theoretical. This changed on Oct. 3, 1952, when the English tested their first nuclear bomb off the coast of Australia.

The race during the '50s started off quickly, but the real dangers didn't become evident until the next decade. To learn about nuclear weapons in the '60s, read on.

The first half of the 1960s turned out to be one of the most trying eras of the nuclear arms race. Between 1960 and 1964, both France and China joined the nuclear weapons "club" by testing their own designs. The Soviets tested the most powerful bomb ever to explode, a 58-megaton atmospheric hydrogen ­bomb.

As President Dwight Eisenhower left office, he warned the nation about the dangers of the military-industrial complex, a broad term that described the large network of individuals and institutions working on weapons and military technology. A growing awareness of tensions between nations, especially the United States and Russia, was only adding more heat to the Cold War. At one point, Americans were even encouraged by President Kennedy to build or buy their very own bomb shelters to avoid the dangers of a nuclear attack. People listened, and a year-long frenzy of shelter construction consumed many Americans.

One of the first major scares of the race began with the failed Bay of Pigs invasion in Cuba in April 1961. New president John F. Kennedy had approved a CIA plan to overthrow the Cuban government and replace the country's leader, Fidel Castro, with a politically friendly, non-communist government. The CIA trained a group of Cuban exiles to invade the country, but the invasion ended quickly once bombers missed targets and the invaders were either killed or captured

This military error embarrassed Kennedy, but it led to a much more dangerous situation. The next year on Oct. 14, a U-2 bomber flying over Cuba sighted Soviet nuclear missile sites under construction, and what is known as the Cuban Missile Crisis began. The missiles were pointed at the U.S., and a nuclear warhead could easily reach America in a short amount of time.

From Oct. 16 to 29, the world watched as President Kennedy and Communist Party leader and Soviet premier Nikita Khrushchev nervously negotiated the removal of the missiles. The Soviets finally agreed to withdraw the weapons, but this marked the closest the world had come to nuclear war.

By this point, both the U.S. and the Soviet Union recognized the concept known as mutual assured destruction (MAD) — if one country made a nuclear attack, chances were good the other would simply strike back, and the destruction of both nations would likely be the only outcome. This was the only thing that kept both nations from attacking each other, and as the '60s ended, more efforts were made toward slowing or stopping the nuclear arms race.

The two rivals installed a "hotline" to facilitate discussion in the event of another close call. In July 1968, the Treaty on the Non-Proliferation of Nuclear Weapons was signed in Washington, D.C., Moscow and London, with the aim of preventing any nation without nuclear weapons from acquiring them. The first Strategic Arms Limitation Talks (SALT I) between the U.S. and Soviet Union also began in Helsinki, Finland, in November 1969, and the world was on its way toward a nuclear détente, a relaxing of tensions and an attempt at understanding.

To learn more about détente during the 1970s, continue reading.

The SALT I sessions continued in the early '70s, and by May 1972 President Nixon and Leonid Brezhnev signed a series of treaties, including the Anti-Ballistic Missile (ABM) Treaty. The limitation of ABMs became an important step — although they were defense systems, an excess of anti-ballistic missiles actually encouraged offense. If one country knew it had a better chance of stopping attacks than the other, it would have less to lose in a nuclear war. With the ABM Treaty, the United States and the Soviet Union agreed to maintain just two ABM sites each.

Despite perceived improvements in international relations, everything wasn't exactly rosy. A U.S. development in nuclear weapon technology during this era was multiple independently targetable reentry vehicles (MIRVs) — single missiles that could target multiple cities with several nuclear warheads. MIRVs could easily overcome a limited defense system comprised of only two ABMs. The ABM Treaty never addressed this innovation, and during the '70s America and the Soviets would add more than 12,000 nuclear weapons to their stocks.

By th­e end of the '70s, tensions between the U.S. and the Soviet Union began to rise once again. A second series of talks ended in 1979 with the signing of the SALT II treaty, which recognized MIRVs and set limits on the number of weapons a country could have and the rate at which technology could move forward. President Jimmy Carter, who originally signed the treaty, pulled out of the agreement in January 1980 when the Soviets invaded Afghanistan, setting the stage for the next difficult decade.

The decade also ended with a scare when the nuclear power plant at Three Mile Island suffered a partial meltdown in 1979. The accident, located near Harrisburg, Penn., caused 140,000 residents to flee the ­area upon hearing news of the first major nuclear power accident. No one was injured or killed during the accident, but the event heightened fears of nuclear power and increased the need for safety regulations.

Alongside the attempt at détente, two more countries joined the nuclear "club" in the '70s. India unexpectedly began testing nuclear technology in 1974 — an underground test on May 18, known as "Smiling Buddha," wasn't a weapon suitable for warfare, and Indian officials declared the trials "peaceful." The test still received negative international attention as yet another country emerged with nuclear capabilities, and the action prompted Pakistan, India's longtime rival, to respond with their own tests soon after.

With the election of President Ronald Reagan in 1981, military spending became a top priority for the United States. Cold War rhetoric increased dramatically, as the Soviet Union was referred to as an "evil empire" by Reagan. In 1983, the president proposed a new, extremely expensive space-based anti-ballistic missile system called the Strategic Defense Initiative (SDI). Also known as "Star Wars," the plan hoped to design a complex anti-ballistic missile system that used technology on the ground and satellites in space to defend the U.S. from airborne nuclear attacks.

T­he controversial program was eventually abandoned because it was too complicated and expensive — after the U.S. spent more than $30 billion, barely any progress was made on the "Star Wars" plan, and many critics pointed out that its science-fiction-based name was appropriate for a system that might never come to fruition. Despite this, the Americans were still far ahead of the Soviets in technology and funds, and Mikhail Gorbachev, Russia's leader at the time, was pushing more for peace and restructuring.

As Soviet-American relations began to improve by the late '80s, the Soviet economy was on the verge of collapse. On Nov. 9, the Berlin Wall fell, finally uniting East and West Germany. The wall was a longtime symbol of the tensions between the Soviets and the U.S., and the Cold War effectively ended two years later when the Soviet Union ceased to exist.

The '90s began with a sense of relief and the feeling that the threat of nuclear war had weakened. The Strategic Arms Reduction Treaty (START I) was quickly reintroduced for consideration — the plan had begun during the Reagan administration, but disagreements led to a standstill on its ratification. Presidents George H.W. Bush and Gorbachev signed the treaty with pens made from melted-down nuclear missiles, as it called for the reduction of nearly 50 percent of each country's nuclear arsenal.­

­Although nations made gradual improvements after the Cold War toward disarm­ament, complications continued to emerge during the '90s and into the 21st century. Nations including China and India continued to test weapons on and off despite a general movement toward the end of such acts. Nine countries are known to have an arsenal of nuclear weapons — the U.S., Russia, Britain, France, China, India, Pakistan, Israel, and North Korea.