B6, key topic 3 - New forms of conflict, 1945–75

Atomic Bombs, 1945

The first turning point came at the end of the Second World War. The United States tested the first nuclear device at Trinity in New Mexico on 16 July 1945. On 6 August 1945 it dropped an atomic bomb on Hiroshima. On 9 August it dropped a second on Nagasaki. Japan announced surrender soon afterwards. The atomic bombings were part of wider pressures, including Soviet entry into the war and Japan’s deteriorating military position; their relative importance remains debated.

The reasons for dropping the bombs are debated, but an Edexcel answer needs to understand the main arguments available to decision-makers in 1945.

The atomic bomb did not simply make a bigger explosion. It changed the relationship between victory and destruction. Before 1945, a state might expect that winning a war meant defeating an enemy's armies and occupying territory. After Hiroshima and Nagasaki, leaders had to think about whether using the most powerful weapons might destroy cities, civilians and political legitimacy as well as enemy forces.

There were also moral and historical arguments against using the bombs. Critics pointed to civilian deaths, radiation sickness, Japan's weakening position, possible alternatives such as blockade or a demonstration, and the danger of beginning a nuclear age. That debate matters because nuclear warfare was never just a technical development. It forced governments to ask what kind of victory was acceptable.

Misconception check: the bombs did not make conventional war disappear. They contributed to the end of one war, but after 1945 armies still fought with tanks, aircraft, artillery, infantry and naval forces across the world.

Arms Race And Delivery

From 1945 to 1949, the United States had a nuclear monopoly. That ended when the Soviet Union tested its own atomic bomb in 1949. The arms race then became a competition not only to own nuclear weapons, but to make them more powerful, more numerous, faster to launch and harder to destroy.

The key developments can be seen as a chain.

Delivery systems mattered because a weapon is only useful if it can reach a target. In 1945 the bomb was delivered by aircraft. By the 1960s, superpowers also had land-based missiles in silos and missile submarines at sea. This made nuclear planning more complex. A bomber could be recalled, but might be intercepted. An ICBM was fast, but once launched it could not be easily stopped. A submarine missile was especially dangerous because the submarine might survive even if land bases were destroyed.

This produced a paradox. The arms race was aggressive because each side built more destructive weapons. Yet some delivery systems were also defended as stabilising because they made retaliation likely. If both sides knew an enemy could still strike back after a surprise attack, starting nuclear war became less tempting.

Other weapons of mass destruction also remained part of post-war thinking. Chemical and biological weapons had already been restricted in use by the 1925 Geneva Protocol, but that did not fully ban development, production or possession. Their delivery methods often overlapped with conventional war: artillery shells, aerial bombs, rockets, missiles or spray systems could all be imagined as ways to spread poison gas, toxins or disease. The 1972 Biological Weapons Convention, entering into force in 1975, showed that biological and toxin weapons were treated as a serious category of mass destruction even when they were not central to every battlefield.

The main lesson is that technology changed both scale and speed. War planning increasingly included the possibility of rapid, long-range destruction rather than only armies meeting on a front line.

MAD, Proliferation And WMD

The most important nuclear theory of the period was mutual assured destruction, often shortened to MAD. It meant that if one nuclear superpower attacked the other, the victim would still be able to retaliate so devastatingly that both societies could be destroyed. In this logic, the best defence was not victory in a nuclear war. It was making nuclear war too dangerous to begin.

MAD depended on three conditions.

This made nuclear war different from conventional war. In a conventional conflict, a government might calculate that it could defeat the enemy army, occupy territory and accept losses. In a nuclear conflict between superpowers, "winning" could mean national destruction. MAD therefore made direct U.S.-Soviet war less likely, but it also made crises terrifying because a mistake, false warning or uncontrolled escalation could be catastrophic.

Nuclear proliferation made the problem wider. The United States tested first in 1945, the Soviet Union in 1949, Britain in 1952, France in 1960 and China in 1964. More nuclear states meant more centres of decision-making, more possible crises and more difficulty controlling the spread of knowledge and technology.

The issue was not only nuclear weapons. "Weapons of mass destruction" usually included nuclear, chemical and biological weapons. Each raised a different fear.

The Nuclear Non-Proliferation Treaty was important because it tried to stop more countries from acquiring nuclear weapons while recognising the five nuclear-weapon states that already had them by the time the treaty was agreed. This was not full disarmament. It was an attempt to manage danger.

The strongest judgement is that nuclear weapons both changed and froze warfare. They changed war because their destructive power was unprecedented. They froze some conflict because superpowers avoided direct nuclear confrontation. But they did not remove violence; they pushed much rivalry into conventional wars, proxy wars and guerrilla conflicts.