Some of the greatest events in human history simply fail to register in popular consciousness. Last year, we rightly heard a terrific amount about the Reformation, or at least, about its early Lutheran phase. But the spring of 2018 actually marks the 400th anniversary of the outbreak of the Thirty Years’ War, another critical event that was at least as significant as the Reformation. The war raged for a full generation, and claimed some eight million lives. In various ways, the conflict profoundly influenced our ideas about politics, diplomacy, military affairs, science, and religion, and it had an immense impact on art and literature. It ensured the survival of Protestantism, and created the state system that endured until the last century. This was a critical event in making Europe as we know it historically, and in shaping the Western consciousness.

For various reasons, the Thirty Years’ War is just a blank for most nonspecialists in the English-speaking world. That question of memory is one of the great gulfs between Continental Europe and the Anglosphere. Europeans long remembered the war’s titanic personalities and events, and commemorated them in both high and low culture. The ghastly wartime experiences of ordinary people are indelibly stamped in European popular imagination through the searing images of printmakers like Jacques Callot, with his Miseries of War series, or the satirical novel Simplicius Simplicissimus, a founding text of German fiction. Those works have, in turn, been used by more modern German writers. Bertolt Brecht’s Mother Courage and Her Children, which is set in Germany in the mid-1630’s, ranks high in most critics’ lists of the greatest works of modern European drama.

In contrast, even the war’s greatest figures remain scarcely known in the Anglo-American world; not even the charismatic warlord Albrecht von Wallenstein, whom Europeans often remember as a kind of proto-Napoleon, is known this side of the Atlantic. No modern-day re-enactors recreate battles like Lützen or Rocroi, and the war is absent from English-language popular culture. Beyond one surprisingly good Michael Caine film—The Last Valley (1971)—there are few fictional treatments. That oblivion is not hard to explain, as the kingdom of England was never formally involved in the war. Despite early efforts to entangle England, her King James I staunchly favored peace. In the event, all four nations of the British Isles supplied many thousands of mercenaries and volunteers to the fighting, and if they had served under a common flag, England would have been a key political and diplomatic player in European affairs. As it was, James showed wisdom. Tragically, his efforts failed in the long term, as European divisions spilled over into the British Isles and did much to spark the devastating civil wars that ruined Britain and Ireland in the 1640’s. For whatever reason, those wars are rarely placed in their proper international context, so that Anglo-Americans regard the Thirty Years’ conflict as some strange European squabble that had nothing to do with them. It all happened somewhere vaguely on the coasts of Bohemia.

The essential context of the war was the fundamental rivalry between Catholics and Protestants, which had detonated so many conflicts since the 1520’s. By 1618, the Catholic powers were in a very strong position. Since Luther’s time, the Catholic Church had staged a powerful restoration in culture and spirituality. Across Europe, Catholics not only survived the Reformation crisis, but from the 1580’s they were making major advances in the process of reclaiming and re-Catholicizing dissident areas. The Catholic Spanish and Portuguese spread their religious and political power over large sections of Africa, Asia, and Latin America, making millions of converts by force or persuasion. The Catholic Church was proudly global, while their Protestant counterparts were largely confined to Northern and Western Europe. When Christians in 1617 recalled Luther’s Reformation, there was no question whether Catholicism or Protestantism seemed destined to flourish most. The key question was whether Protestantism would even survive.

Europe in 1618 faced a perfect storm of diplomacy and dynastic conflict, which raised existential issues for Catholics and Protestants alike. Politically, the most important theme was the power of the mighty Habsburg dynasty, branches of which ruled Europe’s two greatest states: the Spanish Empire and the Holy Roman Empire. Both branches were devoutly Catholic. The great rival of Spain was the Netherlands, which had fought a lengthy war of independence from the 1560’s onward. In 1609, the Spanish and Dutch signed a 12-year truce, which effectively recognized the independence of the Netherlands, but European diplomats nervously anticipated the truce’s expiration in 1621. Although France’s ruling dynasty was Catholic, the country dreaded any further expansion of Habsburg power.

The other potential center of crisis was the Holy Roman Empire (hereafter referred to simply as the Empire), which had its heart in the German-speaking lands, but which cast its influence much further afield. The imperial office was elective, and was decided by a group of great aristocrats and prelates. Ever since 1440, that office had been in the posses- sion of the Habsburg dynasty, but that long-unchallenged assumption appeared under threat. In 1618, the obvious heir was the very devout Habsburg prince Ferdinand II, who had a quite plausible game plan for the extinction of European Protestantism. He had already worked hard at re-Catholicizing his Austrian lands, and he then gained the crown of Bohemia. From that base, he had only to await the passing of his cousin, the Emperor Matthias, and then he would surely succeed to imperial rule.

But 1618 was a tumultuous year. Fearing Ferdinand’s intolerant rule, the Protestant Bohemian elite rebelled that May and invited Frederick, the Protestant elector of the Palatinate, to be their king. (The Palatinate was a Rhineland state with its capital at Heidelberg.) But such a move was profoundly destabilizing, as it would shift the balance of electoral power within the Empire to the Protestant cause. Just as Protestants dreaded Catholic rule, so Catholics feared Protestant subversion. One way or another, if Habsburg power was to survive, Frederick had to be stopped from ruling Bohemia.

The war now began in earnest. Catholic forces won dramatic early victories, conquering both Bohemia and the Palatinate. When Ferdinand actually did become emperor in 1619, he undermined Protestantism as systematically as his enemies feared, advancing his policy of spiritual reconquest in the newly acquired territories. Over the next decade, the war expanded steadily in scope and scale, involving the Netherlands, Spain, and multiple German states, as well as the Empire itself. Catholic military power triumphed repeatedly, under generals like Counts Tilly and Wallenstein. By 1630, Catholic battle standards advanced to the Baltic, raising the question of where, if anywhere, might still be considered safe Protestant territory.

It was this very overreach that prevented a Habsburg triumph. Tilly’s successes provoked a counterstroke by the Swedish King Gustavus Adolphus, who smashed Catholic forces at Breitenfeld in 1631, and thereby established Sweden as a great European power for two generations. Gustavus died in battle the following year, but France increasingly became involved in the anti-Habsburg cause. By the 1640’s, France acquired the military power that allowed her to dominate European battlefields for two generations.

By 1641, it was clear that neither side could win outright victory, and that only diplomacy could resolve the bloody stalemate. Several years of intense fighting ensued before the powers signed their comprehensive peace in Westphalia, in 1648.

The war’s most immediate results were straightforward, and of defining significance for later Western history. Although neither side emerged as a clear victor, it was no longer possible to contemplate total victory for either Catholics or Protestants, nor the extirpation of either side, as had seemed all too possible in 1618. When a monument was erected at Breitenfeld in 1831, it commemorated “Freedom of Belief for the World, Rescued at Breitenfeld by Gustavus Adolphus, Christian and Hero” (“Glaubensfreiheit für die Welt, rettete bei Breitenfeld . . . ”), and the boast carries weight. Likewise, both Spain and the Empire ended the war so weakened that Europe never again needed fear a continental Habsburg supremacy. In all senses—politics, economics, culture—Europe’s center of gravity shifted decisively to its northern and western regions.

Other consequences, though, were not so immediately apparent, and describing the war in terms of campaigns, battles, and treaties gives no sense of its larger impact. Not only was the war so unspeakably prolonged, but it was fought in ways that raised real concerns for the survival of European civilization. The year 1640 has a fair claim to rank as the worst year in European history before 1940.

States of the time were utterly incapable of paying or supplying armies, who had to live off the land—in other words, they seized food and treasure from every community through which they passed. States contracted with private armies, which could be immense: Wallenstein dominated much of Central Europe with a semiprivate force up to 100,000 strong, until a nervous Emperor Ferdinand had him assassinated in 1634. The desperate effort to pay for war caused the collapse of financial systems in several states, with resulting popular risings and revolutions against royal authority.

Armies faced no legal constraints in terms of their treatment of civilians, especially when religious fanatics on both sides were calling for the annihilation of rival believers as infidels. Massacres and sacks were commonplace, the most notorious being the Catholic destruction of Magdeburg in 1631. Some 25,000 perished in “Magdeburg’s Sacrifice.” A 17th-century landscape of war was a nightmare theater of plunder and rape, famine and cannibalism, in which civilization all but ceased to function. German lands especially suffered horrific damage, from which they took decades to recover. In all, Germany probably lost a third of her population, a level of destruction we today associate with nuclear warfare. Inevitably, ordinary people sought scapegoats for the disasters of the age, making the post-1625 decade one of the bloodiest eras ever in European witch-hunting.

Much of European history over the following two centuries can be understood only in light of this horrific experience, and the overwhelming need to prevent a recurrence. At the international level, this meant the so-called Westphalian system, in which nation-states were paramount, and they had recognized boundaries. And if the Empire maintained its notional supremacy over subject realms, those kingdoms and electorates acted very much like freestanding countries. We now enter the age of such long-famous states as Saxony, Bavaria, and Brandenburg-Prussia. Europe’s states agreed on a rough balance of power, orchestrated through successive congresses and treaties, and reinforced by ties of dynastic marriage and kinship. Although disrupted by the French Revolutionary wars, that model persisted in broad outline until the last century.

Domestically, the chaos of the Thirty Years’ War era led directly to absolutism, which remained the dominant political order in Europe until 1789. So dreadful was the violence of the radical years that elites were willing to suspend or abolish their representative institutions, their parliaments or estates, to place all power in a royal court. Again, this development marked a vital contrast between parliamentary England and the absolutist Continental powers, although even England came close to losing her parliament later in the 17th century. The revamped monarchies operated according to a new and far more exalted ideology of royal power, which drew heavily on classical symbolism, portraying the monarch as Jupiter or the Sun. These ideas were symbolized by the creation of spectacular new palaces like that of Versailles and its many imitators. The emerging state order demanded a new and sophisticated profession of go-betweens and emissaries—of diplomats and ambassadors.

But if the war fostered the growth of absolutist kingship, it also offered the means by which such overweening power could be challenged and overcome. Anarchy and the near collapse of the state order inspired a revolution in political thought, as thinkers explored the basis of authority and power, of rights and liberties, and the religious and ethical obligations of states. The diverse conclusions that such philosophers drew laid a firm foundation for the political thought of the Enlightenment, the beginnings of which are conventionally dated to 1648. So much of what we think of as the origins of the modern West can be traced to this era.

These writers had witnessed a generation of bloodshed, massacre, and assassination, when the boundaries separating states from bandit gangs seemed hard to draw. When so many moral assumptions were collapsing, what were the foundations on which society could and should be reconstructed? What were the core elements of the European Christian tradition, which separated it from pagan barbarism? What were the rights of individuals? In 1625, at the height of the Dutch-Spanish wars, Hugo Grotius published his book On the Law of War and Peace, which became the basis of modern thought about war and international law. Among other things, Grotius’ book advanced civilized principles that would still be true even without the sanction of either of the warring faiths of the time, or etsi deus non daretur—even if God did not exist. This was revolutionary thought for times of crisis.

It was in 1651 that Thomas Hobbes published his Leviathan, a daringly frank manifesto for absolutism, which nevertheless presented critical ideas about individual rights and equality, and representative government. That, in turn, inspired the work of John Locke. Hobbes and Grotius profoundly influenced German thinker Samuel von Pufendorf, and through him, their ideas saturated the American Founding Fathers. The liberal thought that inspired the American Revolution and the constitutional debates was formed precisely in reaction to the lawless savagery of the Thirty Years’ War.

In other ways, too, memories of the war still influenced political ideology and sparked intellectual debate centuries after 1648. In German-speaking lands, debates over the war profoundly shaped the emergence of nationalism and liberalism. Generations of scholars argued over the reasons for the catastrophe, and speculated whether Wallenstein could or should have led a precocious leap to authentic German nationhood. Besides Goethe, the towering genius of the German Enlightenment was Friedrich von Schiller, who wrote a substantial history of the war. He followed that with his vastly influential trilogy of plays about Wallenstein. Schiller’s writings supplied the foundation for 19th-century literary struggles, as Protestants and Catholics argued furiously over the war’s implications for modern-day German nationalism and unity. Most of the participants in these debates took the lesson that Germany had been fatally weakened by becoming the plaything of foreign powers and interests, and that such ruinous dabbling should never again be permitted.

In matters of science and natural philosophy likewise, the Thirty Years’ War coincided neatly with the opening stages of the Enlightenment, and it is not hard to discern connections. It is unsettling to think that René Descartes was working at the time of the war’s bloodiest stages in the 1630’s and 40’s, as were some of the most active minds in the Netherlands and Britain. Partly, this represented a reaction against the mutually destructive fanaticism of the era, and a quest for absolutes and universal principles. That quest came to fruition with the formation of the English Royal Society in 1660, and all the subsequent scientific inquiry inspired by this “invisible college.” Over the following decades, rational and scientific thinkers often justified their endeavors as reactions against the brutality of the war years, and the blind irrationality of the witchcraft trials. As the popular phrase had it, Light emerged after Darkness—post tenebras lux—and the Thirty Years’ War was undeniably the tenebras in question. The rhetoric of progress and modernity was born.

The war’s other great legacy was in military affairs. For 250 years, the battles of Wallenstein and Gustavus were the great set pieces that fascinated latter-day generals from Napoleon to Stonewall Jackson. Napoleon himself often shaped his actions according to the examples he found in the Thirty Years’ War, and particularly admired Wallenstein for his abilities in logistics and organization. Seventeenth-century military ideas were popularized by Carl von Clausewitz, whose On War remains a mainstay of military academies. Clausewitz was another Wallenstein devotee, and Schiller’s plays about that hero were his favorite reading.

But Gustavus was no less a revolutionary, whose innovations around 1630 became so standard for most later armies that we tend to forget how radical were the underlying principles. Gustavus brought a uniformed and highly disciplined Swedish force, lightly equipped and heavily committed to mobility, speed, and maneuver. Rather than using his cavalry in all-out charges, Gustavus had his Swedish horsemen fire their pistols and then withdraw to reload, while infantry were deployed in thin lines to maximize firepower. Front lines fired their muskets and then withdrew behind the next line in order to reload, with the rolling fire later made famous by the British Square of Victorian times. Historians debate the title, but Gustavus is often called the Father of Modern Warfare.

Each generation reads the Thirty Years’ War in its own way, applying its own values and obsessions, and some aspects of that conflict speak to us today. Yes, we can still condemn the religious fanaticism that drives war and massacre, but the war also teaches some sobering lessons of realpolitik. To take one such lesson, the states that begin a war—any war—are not necessarily all that relevant to its final outcome. The Thirty Years’ War began with the two all-powerful Habsburg states, both of which still existed in 1648, but by that point they operated in a whole new political geography. They faced a very potent competitor in France, a country that would soon seek European hegemony. Other brash rising newcomers included Sweden and Brandenburg-Prussia, under its Hohenzollern dynasty. The French actively favored the Hohenzollerns as a counterbalance to the Habsburgs: After all, what possible harm could Hohenzollern Prussia ever do to proud France? This was a world unimaginable to the most acute analysts of 1618. Wars have a bad habit of reshaping the world in a way that leaves once-great powers high and dry on the global scene.

So who won the Thirty Years’ War? Not the people who started it.

Any modern state contemplating war could also learn much from the example of Spain, which in 1618 was an authentic global empire. But wars then beckoned, first in the Netherlands and then further afield, and the conflicts lasted for decades. In the early 1640’s, Spain suffered a political and fiscal crisis on a scale scarcely paralleled in modern European history. Public finances collapsed, and restive areas of Spain sought their freedom: Portugal successfully, and Catalonia less so. A Spanish state barely succeeded in staggering to the conference table in 1648. Early modern states simply could not afford prolonged warfare. It remains open to question whether their modern successors are much more capable.

Studies of the Thirty Years’ War should be required reading not just for would-be military officers, but for anyone guiding the fortunes of modern democracies, and especially their economies.