The Thirty Years’ War is commonly divided by historians into four different intervals/periods in which various Western European regions and countries became dominant in the fighting. The first part of the war, which lasted from 1618 until 1622, took place mostly in Bohemia, a region which today is part of Germany. The Bohemian Period first erupted when Ferdinand, the archduke of Styria – who in 1619 would also become Ferdinand II, Holy Roman Emperor – took over the throne of Bohemia and began persecuting Protestants. Outraged, the Bohemian Protestants rose up to throw off Ferdinand’s rule, drawing in various other Western European powers in the process. The Danish Period (1625-1629) broke out when King Christian IV of Denmark came to the Bohemian Protestants’ rescue by attempting to invade the Germanic region. Next, in 1630, came the Swedish Period, in which King Gustavus Adolphus II of Sweden assumed leadership of the main Protestant forces. A brilliant military strategist, King Adolphus led the Swedish and other Protestant armies to numerous victories against Ferdinand’s Catholic armies. Eventually, in 1635, several German Protestant states (led by Saxony) entered into the Peace of Prague with Ferdinand and dropped out of the conflict. But Sweden, buoyed by fresh support from France and the Netherlands, refused to back down and so the final period of the war, the Swedish/French, erupted. Lasting for thirteen more years, this interval saw some of the bloodiest fighting of the entire conflict, especially once the Spanish Army got involved (on the side of the Holy Roman Emperor).

Historians consider the Battle of Breitenfeld to be the turning point of the Thirty Years’ War. The Battle of Breitenfeld occurred in 1630, right at the opening of the Swedish period of the conflict. At this point, King Gustavus Adolphus II of Sweden had just entered the war and he was eager to put his famous military mind and strong army to the test. However, the Holy Roman Emperor, Ferdinand II, had recently chosen a new leader for his armies – Albrecht of Wallenstein, a Protestant mercenary who had recently won several brutal victories in Denmark and who seemed unstoppable. Shrewdly, King Adolphus allied himself with the leaders of the Germanic territories Brandenburg and Saxony and their combined military might crushed Wallenstein’s forces at the Battle of Breitenfeld. Crucial to the Swedish/Brandenburg/Saxony victory were the Swedish King’s new battlefield innovations – King Adolphus made his artillery, infantry, and cavalry units all quite mobile and also taught them his own fearsome “fire and charge” strategy. The defeat of his forces at Breitenfeld came as a complete shock to the Holy Roman Emperor and he lost confidence in Wallenstein as an effective general. In 1634, the Emperor actually had Wallenstein assassinated, a decision which was motivated even further by revelations that the mercenary had been attempting to make backroom peace deals with the Protestant army.

Finally, the Thirty Years’ War came to an end in 1648 with the Treaty of Westphalia. The Treaty upheld the Peace of Augsburg by re-stating that the ruler of every country and/or region was allowed to freely (without external interference) choose his/her people’s national religion. The Treaty also recognized the independence of each Germanic territory, of which Brandenburg (later known as Prussia) and Austria would become the most influential. Legal independence was also granted to the Swiss Confederacy (aka modern Switzerland) and the United Provinces of the Netherlands. Perhaps most importantly for Europe’s future peace, Calvinism was recognized as a fully legal and protected religion, just like Lutheranism and Catholicism had been for many years. Pope Innocent X opposed this last agreement but the other rulers, desperate for peace, overruled his objections.

Today, many historians rank the Thirty Years’ War as the second most destructive event in all of pre-modern European history (the time period before the Industrial Revolution). Naturally, the Black Death holds the number one spot. The Thirty Years’ War earned this reputation because of the massive amount of causalities, both military and civilian, that resulted over the long years of warfare. Each leader urged his men to fight ruthlessly, employed brutal battle tactics, and encouraged widespread looting and plundering of any captured territories. The fierce nature of these techniques, combined with the religious hatred that raged through both sides, guaranteed that any civilian caught in the crossfire stood a good chance of being killed, even after a battle had ended. Casualty counts were especially high in the Germanic region, where historians estimate that by the time the Treaty of Westphalia had been signed in 1648, one third of the total population had been killed.

In 1642, the long years of animosity between Parliament and King Charles I erupted into civil war. The final push into armed conflict came when the King personally led a military invasion of Parliament, seeking to capture and imprison the most vocal of his critics within that body. Although the King’s effort failed, he promptly began to assemble his army and so Parliament, outraged by the incursion, raised their own forces. Soon enough, the two forces met on the battlefield and would continue to clash in numerous battles for the next four years. The King’s men became known as “Cavaliers” (because of their formal military training), while Parliament’s soldiers were called “Roundheads” (because of the distinctive shape of their helmets). Ultimately, Parliament would win the war, partially owing to their alliance with Scottish rebels in 1643. Yet perhaps the single most crucial factor that led to Parliament’s victory was the leadership of one man: Oliver Cromwell. Cromwell was an English squire who rose to prominence through the Parliamentary forces due to his military cunning, strong leadership, and strict discipline. Cromwell was a devout Puritan and he intended that Parliament’s victory over the King would lead to formal legal acceptance of dissenters by the English government.

The Peace of Augsburg, which first took effect in 1555, put an end to the battles that had been waged between various Protestant armies against the Holy Roman Emperor Charles V over a period of nearly thirty long years. The Peace included various conflict resolutions but its most important term was the adoption of the principle that from now on, the leader of each Western European region (from Switzerland to Denmark to Germany) was able to freely choose the religious allegiance of his own region. No outside influence or external force was allowed to interfere with this freedom and any region’s dissenters were permitted to immigrate to another area in which their religion had been selected as the official norm. Under the Peace of Augsburg, Lutheranism was officially granted legal protection and the regional split between Protestantism and Catholicism was therefore firmly established.

As part of his strategy to increase France’s status and secure its borders, in 1667 King Louis XIV invaded the neighboring territories of Flanders and the Franche-Comte. Prior to the invasion, tensions between these territories, France, and the Spanish Netherlands had reached a boiling point after King Louis claimed that his first wife (Marie Therese) was the rightful heir to the Spanish Netherland’s throne. (The Spanish Netherlands were separate from the United Provinces of the Netherlands.) When neither the government of the Spanish Netherlands or any other surrounding provinces agreed to support his claim, Louis decided to seize what he wanted by force and so in 1667 he sent his armies to simultaneously invade Flanders and the Franche-Comte (two areas which France had long coveted). This conflict became known as the War of the Devolution. While France’s invasion was initially successful, ultimately France was forced to retreat from Flanders by the armies of England, Sweden, and the United Provinces of the Netherlands. These three nations banded together, in the so-called Triple Alliance, to force out France’s army and hopefully put an end to Louis’s ambitions. Yet in spite of his forced retreat from Flanders, Louis was far too militarily strong to ignore entirely. In the Treaty of Aix-la-Chapelle, which formally ended the War of the Devolution, Louis was able to gain control over several towns that had once belonged to the Spanish Netherlands, as a sort of peace offering that the Triple Alliance hoped would keep the French king satisfied and prevent further confrontations.

In spite of the concessions made to him in the Treaty of Aix-la-Chapelle, King Louis XIV was not content with the amount of territory under French control. As part of his plan to secure France’s borders, he began scheming to conquer several of the areas immediately outside of France’s borders, which he intended to use as buffer zones against foreign invasions. In 1672, Louis sent his French army to invade the Netherlands (both the Spanish Netherlands, which were controlled by the Hapsburg dynasty, and the independent United Provinces of the Netherlands). Alarmed by Louis’s second invasion of the region, William of Orange of the Netherlands joined forces with the Holy Roman Emperor, Spain, and the leaders of the territories of Lorraine and Brandenburg to attempt to defeat the Sun King’s army once and for all. However, France’s army was truly a large and formidable force – Louis had spent massive amounts of money recruiting more soldiers, investing in new methods of training, and furnishing his men with new, top-notch weapons and armor. Consequently, the coalition forces, led by Prince William of Orange, were unable to decisively defeat the French army. Ultimately, the conflict ended in a stalemate. The concluding peace treaty, known as the Peace of Nijmwegen, once again gave Louis several advantageous benefits. Most importantly, this Peace gave France control over the territory of Franche-Comte, which Louis and his royal ancestors had long coveted.

Out of the many military conflicts during his reign as King of France, the War of the Spanish Succession was Louis XIV’s most devastating military blunder. Unlike past conflicts, such as the Nine Years’ War and the War of the Devolution, Louis committed several fatal blunders which terribly weakened his army and robbed France of any possible gains from the conflict. The war was triggered by the death of King Charles II of Spain, who did not have any children of his own. He passed the throne to Philip of Anjou (who became Philip V of Spain), who also happened to be Louis XIV’s grandson. This alarmed many of Spain’s neighbors, including England and the Holy Roman Empire, who all worried that Louis would be able to control his young grandson and manipulate him into joining forces to conquer all of Europe, finally realizing Louis’s aggressive military ambitions for France. To prevent such a development, England, the Holy Roman Empire, the United Provinces of the Netherlands, formed the Grand Alliance and declared that the Holy Roman Emperor was hereditarily entitled to part of the Spanish Empire. Perhaps inevitably, war brought out soon after but things went poorly for Louis’s army almost immediately. All of Louis’s past conflicts had drained the royal treasury and the King didn’t have enough funds left to purchase new weapons, updated armor, or to adequately train new soldiers and generals. Consequently, the French army was poorly trained, poorly led, and equipped with old-fashioned weapons and outdated tactics. They won almost no battles at all, especially whenever the mighty and well-trained English army was involved. The war ended in a stalemate in 1714 but France gained no territories or promises in the resulting peace treaty – and Louis was not strong enough to insist otherwise. He passed away one year later.

Today, the Prussian King Frederick William I is credited by historians with building the strongest, largest, and overall best army in all eighteenth century Europe. Frederick William I inherited his love for the military from his grandfather and namesake, Frederick William, but he took his grandfather’s military buildup to an entirely new level. Frederick William I believed that in order for Prussia to exercise firm domestic control and to win respect (and even fear) internationally, the nation must have the mightiest army possible. This idea soon developed into an obsession and the King spent most of his reign focused pretty much entirely on military affairs (he even re-organized his government bureaucracy according to military rules). When Frederick William I took the throne in 1713, the Prussian army included about thirty-nine thousand soldiers, but by the time of his death in 1740, the army had expanded to over eighty thousand men. Frederick William I favored his military men in all things: special laws and rules applied just to members of the military and military membership quickly came to be considered the highest form of social class in Prussia, with many Junkers (noble landlords) competing to become officers. The King’s military buildup, reforms, and policies completely fused together the Prussian state, Junker class, and the military, so that Prussia became entirely inseparable and even inoperable without its army. But curiously enough, Frederick William I refused to deploy his army into any actual combat situations; his soldiers were for show only, a tool to control the Prussian people and impress and intimidate foreign powers.