War is the most complex, physically and morally demanding enterprise we undertake. No great art or music, no cathedral or temple or mosque, no intercontinental transport net or particle collider or space programme, no research for a cure for a mass-killing disease receives a fraction of the resources and effort we devote to making war. Or to recovery from war and preparations for future wars invested over years, even decades, of tentative peace. War is thus far more than a strung-together tale of key battles. Yet, traditional military history presented battles as fulcrum moments where empires rose or fell in a day, and most people still think that wars are won that way, in an hour or an afternoon of blood and bone. Or perhaps two or three. We must understand the deeper game, not look only to the scoring. That is hard to do because battles are so seductive.

War evokes our fascination with spectacle, and there is no greater stage or more dramatic players than on a battlefield. We are drawn to battles by a lust of the eye, thrilled by a blast from a brass horn as Roman legionaries advance in glinting armour or when a king’s wave releases mounted knights in a heavy cavalry charge. Grand battles are open theatre with a cast of many tens of thousands: samurai under signal kites, mahouts mounted on elephants, a Zulu impi rushing over lush grass toward a redcoat firing line. Battles open with armies dressed in red, blue or white, flags fluttering, fife and drums beating the advance. Or with the billowing canvas of a line of fighting sail, white pufferies erupting in broadside volleys. Or a wedge of tanks hard-charging over the Russian steppe. What comes next is harder to comprehend.

The idea of the ‘decisive battle’ as the hinge of war, and wars as the gates of history, speaks to our naive desire to view modern war in heroic terms. Popular histories are written still in a drums-and-trumpets style, with vivid depictions of combat divorced from harder logistics, daily suffering, and a critical look at the societies and cultures that produced mass armies and sent them off to fight in faraway fields for causes about which the average soldier knew nothing.

Visual media especially play on what the public wants to see: raw courage and red days, the thrill of vicarious violence and spectacle. This is the world of war as callow entertainment, of Quentin Tarantino’s Inglourious Basterds (2009) or Brad Pitt in Fury (2014). It’s not the world of real Nazis or real war.

Battles also entice generals and statesmen with the idea that a hard red day can be decisive, and allow us to avoid attrition, which we all despise as morally vulgar and without redemptive heroism. We fear to find only indecision and tragedy without uplift or morality in trench mud, or roll calls of dead accumulating over years of effort and endurance. Instead, we raise battles to summits of heroism and generals to levels of genius that history cannot support. Though some historians might try, celebrating even failed campaigns as glorious. Prussia is wrecked, yet Frederick is the greatest of Germans. France is beaten and an age is named for Louis XIV, another for Napoleon. Europe lies in ruin, but German generals displayed genius with Panzers.

Whether or not we agree that some wars were necessary and just, we should look straight at the grim reality that victory was most often achieved in the biggest and most important wars by attrition and mass slaughter – not by soldierly heroics or the genius of command. Winning at war is harder than that. Cannae, Tours, Leuthen, Austerlitz, Tannenberg, Kharkov – all recall sharp images in a word. Yet winning such lopsided battles did not ensure victory in war. Hannibal won at Cannae, Napoleon at Austerlitz, Hitler at Sedan and Kiev. All lost in the end, catastrophically.

There is heroism in battle but there are no geniuses in war. War is too complex for genius to control. To say otherwise is no more than armchair idolatry, divorced from real explanation of victory and defeat, both of which come from long-term preparation for war and waging war with deep national resources, bureaucracy and endurance. Only then can courage and sound generalship meet with chance in battle and prevail, joining weight of materiel to strength of will to endure terrible losses yet win long wars. Claims to genius distance our understanding from war’s immense complexity and contingency, which are its greater truths.

Modern wars are won by grinding, not by genius. Strategic depth and resolve is always more important than any commander. We saw such depth and resilience in Tsarist Russia in 1812, in France and Britain in the First World War, in the Soviet Union and the United States during the Second World War, but not in Carthage or overstretched Nazi Germany or overreaching Imperial Japan. The ability to absorb initial defeats and fight on surpassed any decision made or battle fought by Hannibal or Scipio, Lee or Grant, Manstein or Montgomery. Yes, even Napoleon was elevated as the model of battle genius by Clausewitz and in military theory ever since, despite his losing by attrition in Spain, and in the calamity of the Grand Armée’s 1812 campaign in Russia. Waterloo was not the moment of his decisive defeat, which came a year earlier. It was his anticlimax.

Losers of most major wars in modern history lost because they overestimated operational dexterity and failed to overcome the enemy’s strategic depth and capacity for endurance. Winners absorbed defeat after defeat yet kept fighting, overcoming initial surprise, terrible setbacks and the dash and daring of command ‘genius’. Celebration of genius generals encourages the delusion that modern wars will be short and won quickly, when they are most often long wars of attrition. Most people believe attrition is immoral. Yet it’s how most major wars are won, aggressors defeated, the world remade time and again. We might better accept attrition at the start, explain that to those we send to fight, and only choose to fight the wars worth that awful price. Instead, we grow restless with attrition and complain that it’s tragic and wasteful, even though it was how the Union Army defeated slavery in America, and Allied and Soviet armies defeated Nazism.

With humility and full moral awareness of its terrible costs, if we decide that a war is worth fighting, we should praise attrition more and battle less. There is as much room for courage and character in a war of attrition as in a battle. There was character aplenty and courage on all sides at Verdun and Iwo Jima, in the Hürtgen Forest, in Korea. Character counts in combat. Sacrifice by soldiers at Shiloh or the Marne or Kharkov or Juno Beach or the Ia Drang or Korengal Valley were not mean, small or morally useless acts. Victory or defeat by attrition, by high explosive and machine gun over time, does not annihilate all moral and human meaning.

The Allure of Battle: A History of How Wars Have Been Won and Lost by Cathal Nolan is out now through Oxford University Press.