The 81st anniversary of the atomic bombing of Hiroshima was commemorated at a time when international relations are confronting nuclear weapons in ways that differ significantly from the past. On August 6, 1945, the United States carried out an atomic bombing of Hiroshima, killing around 140,000 Japanese people.

Three days later, on August 9, the city of Nagasaki was subjected to an atomic bombing, killing approximately 70,000 Japanese people. The deaths of around 210,000 people and the injury of another 100,000 undoubtedly marked not only a turning point in the history of World War II, but also a turning point in the history of international relations.

Over the past eight decades, the nuclear factor has remained a persistent element in international affairs. The world after Hiroshima and Nagasaki is a world of nuclear weapons, and contemporary international relations cannot be understood without understanding the developments surrounding nuclear weapons.

But how can the relationship between nuclear weapons and contemporary international relations be examined and analyzed? The answer is that nuclear weapons have profoundly influenced the way international relations are understood and managed. Thus, the relationship is not limited to one or two nuclear issues; rather, we are confronted with a whole range of interconnected issues and dynamics.

For analytical purposes, at least three broad dimensions can be identified in the relationship between nuclear weapons and international relations: the humanitarian and ethical dimension, the political and strategic dimension, and the dimension of new actions and emerging trends.

The Humanitarian and Ethical Dimension

From a humanitarian and ethical perspective, the catastrophe that occurred in Hiroshima and Nagasaki is incomparable to any other incident or event in the history of warfare. Yes, it was nuclear technology that had been developed in the United States under the Manhattan Project. But the decision to use that technology to cause the widespread destruction of cities was ultimately made by U.S. President Harry Truman.

It was a series of human decisions that resulted in the mass killing of other human beings. Over the past several decades, the historiography surrounding the use of nuclear weapons against Japan has been revisited, raising a number of unanswered questions. One of the most important is whether the atomic bombings were actually necessary. Japan had already been strategically weakened and had little prospect of victory. Why, then, did the United States use the atomic bomb? The human dimension of that decision remains of profound importance.

Beyond the question of human responsibility and the decision to launch the atomic bombings, the killing of more than 200,000 people has generated successive waves of opposition to the use of nuclear weapons around the world. It can therefore be argued that a global movement of anti-war and anti-nuclear activists has emerged.

Active non-governmental organizations and civil-society groups have formed an important part of the global anti-nuclear movement. Their anti-war activities have focused on two major areas. One is the ethical dimension: the argument that nuclear war and the use of nuclear weapons are fundamentally immoral.

The other is the legal dimension. One of the most prominent legal developments was the request for an advisory opinion from the International Court of Justice in 1996 concerning the legality of the threat or use of nuclear weapons. The advisory proceedings themselves, including Iran's position, involved significant legal considerations. Humanitarian opposition to the use of nuclear weapons, as a powerful current, will continue to play a role in international affairs.

The Political and Strategic Dimension

But this is not the whole story. Following the use of nuclear weapons, a substantial body of political and strategic literature emerged concerning nuclear weapons. The production, possession, and development of nuclear weapons introduced a specialized set of concepts and terminology into the field of international relations.

The most important strategic concept is nuclear deterrence, which views nuclear weapons as a means of deterring war. In this context, the concept of Mutually Assured Destruction (MAD) is particularly significant. The underlying logic is that if one side uses nuclear weapons, the other side will retaliate, resulting in the destruction of both.

This strategic concept has been particularly important in creating strategic stability among nuclear powers. It is based on the assumption that nuclear deterrence represents a rational calculation of costs and benefits. But are all strategic decisions based on rationality? Is there room for miscalculation?

In the early 1960s, the United States and the Soviet Union came dangerously close to a nuclear confrontation during the Cuban Missile Crisis, when missiles equipped with nuclear warheads were deployed. The crisis ultimately compelled both superpowers to accept the need for nuclear strategic stability.

From a strategic perspective, a broader nuclear framework has emerged that can be described as the nuclear order in international relations. It encompasses norms, institutions, practices, and approaches designed, among other things, to preserve the nuclear superiority of the major powers. Yet this monopoly has been disrupted, and the existing system has developed significant gaps and tensions.

These tensions have rarely been as pronounced as they have been in recent years. One of the most significant developments today is the expiration of the New START treaty between the United States and Russia in 2026, alongside the two sides' apparent reluctance to commit to further reductions in their nuclear arsenals.

Even more troubling is the normalization of the use of nuclear weapons. Interestingly, this phenomenon can be observed both in Russia and the United States. In Russia, international relations scholar Sergey Karaganov has argued that the use of tactical nuclear weapons in the war in Ukraine may be necessary. In the United States, the possible use of tactical nuclear weapons in regional conflicts has increasingly entered public and strategic debate, contributing to its normalization.

Whatever the case, nuclear weapons have a direct, distinct, yet multilayered relationship with contemporary international relations. The anniversary of the use of nuclear weapons in Hiroshima and Nagasaki provides an opportunity to reflect on this relationship, to understand its different dimensions, and to consider how it can be managed.