Despite the best efforts of military planners and strategists to keep their skills current, there are certain continuities in the nature of war. This is not simply a matter of practice and learning, but of human nature. We have a tendency to seek patterns and predictability in our encounters with conflict, even while acknowledging that every fight is unique. This is why seasoned soldiers can still recall the harrowing details of an individual battle, but struggle to describe the overall pattern of a campaign.

This is also why the question of what causes war remains one of the most intractable for historians. The answer largely depends on one’s philosophy about determinism and free will. Some scholars see a natural need for powerful states to use force, with their own interests and values, to prevail over those of weaker powers. Others see bellicosity and misunderstanding as major contributors to war.

Another key factor in the onset of war is the availability of resources. Early civilizations fought for control of critical foodstuffs, water, and mineral deposits that were necessary for survival, trade, and economic growth. This issue continues to be a central driver of conflict today, with territorial disputes over the control of natural resources, illicit economic gain, and global climate change.

A significant part of the conduct of war consists of calculating the relative strength and potential of opponents, whether through conventional tactics and strategy or more sophisticated espionage and intelligence operations. This calculation is sometimes formalised in doctrine or militarised as drills and procedures, but it often takes place at a more informal level through discussions between commanders, politicians, or the media.

While these calculations are essential for the conduct of war, they can also be dangerous. When they lead to a misreading of the motivations and intentions of adversaries, or the failure to consider the limits of a force’s capacity to achieve its objectives, it can trigger a war that would have been avoidable.

There are times when the calculus of war shifts dramatically, owing to a power shift or a sudden opportunity to exploit an opening. Such shifts and opportunities are often the root of long, bloody conflicts in history, from World War I to the war in Ukraine.

As the world has become increasingly crowded and complex, so too have the factors that contribute to conflict. A number of new challenges have emerged: the rise of non-state actors with international terrorist and criminal groups; a breakdown in global governance and rule of law by rogue state actors; and, for some, the loss of faith in political institutions and a belief that war is inevitable. Each of these challenges presents its own dilemmas, but they all underscore the need to rethink the nature and causes of war.