7.3 War and Peace

The most destructive thing humans do

War is one of the most destructive activities humans engage in. Throughout history, armed conflicts have killed hundreds of millions of people, displaced whole populations and destroyed civilisations. And yet war has been a near-constant feature of human societies, which raises one of the oldest and hardest questions: why do humans go to war?

The study of war and peace sits at the heart of international relations. Political scientists, historians and philosophers have long debated the causes of war, the conditions under which force can be justified, and the best ways to build lasting peace. In our own era, the very nature of warfare has changed dramatically -- from the trench warfare of the First World War to the drone strikes and cyber-attacks of the twenty-first century. Understanding war means examining it from many angles: the political decisions that lead to conflict, the legal frameworks that try to regulate it, the human suffering it causes, and the difficult work of rebuilding societies after the violence ends.

Why wars happen, and how they have changed

Scholars identify a range of factors behind the outbreak of armed conflict, and most wars result from a combination of them rather than any single cause. Among the structural causes are competition for territory, resources or strategic advantage, power imbalances or shifts in the balance of power, and weak or failed states unable to maintain order. Among the political causes are aggressive or expansionist ideologies, authoritarian regimes that suppress dissent and use external enemies to maintain power, and nationalism or ethnic and religious tensions. Among the economic causes are competition for valuable resources like oil, minerals or water, economic inequality and the marginalisation of groups, and the influence of the arms industry. And there are immediate triggers -- an assassination, a border incident, a provocation, miscalculation or misperception of the other side's intentions, or escalation spirals where each side responds to perceived threats. The relative importance of these causes remains a central debate in international relations, which is why a careful, balanced analysis avoids reducing any conflict to a single explanation.

The way wars are fought has also changed dramatically. Interstate conflicts -- wars between states -- have become less common since 1945, while intrastate conflicts, civil wars and internal violence, have become the dominant form; since the end of the Cold War, the vast majority of armed conflicts have been fought within states rather than between them. Asymmetric warfare sees parties of very unequal military strength, with weaker parties using guerrilla tactics, improvised explosives and terrorism to offset their disadvantage, making conventional military superiority less decisive. New technology -- drones, precision-guided munitions, cyber-attacks, artificial intelligence -- is transforming how wars are fought and raising fresh ethical and legal questions about accountability and civilian harm. And through all of it, the human cost remains immense: civilians now bear the brunt of modern conflicts, accounting for most casualties, while displacement, trauma and the collapse of healthcare and education cause suffering that lasts for generations.

Limiting war and building peace

If war cannot always be prevented, it can at least be constrained, and two great frameworks attempt this. International Humanitarian Law (IHL), also called the laws of war, is a set of rules that seek to limit the effects of armed conflict, with the Geneva Conventions of 1949 and their Additional Protocols as the most important instruments. Its key principles are distinction -- parties must distinguish between combatants and civilians, and deliberately targeting civilians is prohibited; proportionality -- the harm caused by an attack must not be excessive in relation to the military advantage gained; military necessity -- force may only be used as far as needed to achieve a legitimate objective; and humane treatment -- prisoners of war and the wounded must be treated humanely. Alongside this legal framework stands Just War Theory, a philosophical tradition reaching back to St Augustine and Thomas Aquinas, which sets criteria for when going to war is morally justified (jus ad bellum: just cause, legitimate authority, right intention, last resort, reasonable chance of success) and how war should be conducted (jus in bello: distinction, proportionality, and no use of inherently evil means).

Building lasting peace after conflict is its own challenge. One important and contested idea is the Responsibility to Protect (R2P), which represents a shift in thinking about sovereignty: it holds that the international community has a responsibility to protect populations from mass atrocities such as genocide, even within a sovereign state's borders. This is genuinely debated -- supporters see it as a moral duty to prevent atrocities, while critics worry it can be misused as a pretext for intervention -- and a fair account presents both concerns. Equally important is transitional justice: the measures used to address past abuses and rebuild after conflict, including trials, truth commissions, reparations and institutional reform. Without confronting the past and rebuilding trust, peace agreements often unravel. Taken together, these frameworks show that humanity has developed real tools to limit war's horrors and to rebuild afterward -- imperfect tools, often unevenly applied, but a meaningful attempt to bring law and ethics to bear on the most destructive of human activities.

In short

War, one of the most destructive of human activities, arises from a combination of structural, political, economic and immediate causes rather than any single one. Its nature has changed: intrastate conflicts and asymmetric warfare now dominate, new technologies are transforming the battlefield, and civilians bear most of the suffering. International Humanitarian Law, embodied in the Geneva Conventions, and Just War Theory provide frameworks for limiting war's horrors through principles like distinction and proportionality. The Responsibility to Protect marks a debated shift in thinking about sovereignty and intervention, while transitional justice is essential for building lasting peace afterward. These tools are imperfect and unevenly applied, but they represent a meaningful effort to bring law and ethics to bear on armed conflict.