It has been famously pointed out that the Holy Roman Empire was neither holy, nor Roman, but it was also not an empire in the sense people expect when hearing the term. In theory, the emperor was the highest prince in Christendom, and his dominion extended the length and breadth of Western Europe. The empire had been created by the papacy in 801 when Pope Leo III famously crowned the supposedly unwitting Charlemagne in Saint Peter's Basilica, intending to recreate the Western Roman Empire. In truth, the imperial power did not extend beyond central Europe, which by the beginning of the 16th century included Germany, northern Italy, and the Netherlands. Even in these lands, however, the emperor struggled to command obedience. His dominion over northern Italy was theoretical only, the cities of the Netherlands were deeply conscious of their ancient rights and privileges, and Germany had long ceased to be compliant. The latter had become a collection of principalities, dukedoms and bishoprics which vied with each other and pursued their own agendas. They were, however, united in only one sense: denying the emperor power and resisting attempts to centralize the government.

This tension was also interwoven with secular politics across the continent. During the 17th century, the Netherlands, despite having only 1.5 million people in 1600, became a global maritime and trading power. By contrast, France at the time had 20 million people, Spain had 8 million, and England had 5 million. Nevertheless, Amsterdam became one of the most important urban centers in the world and the location of the world's first stock market.

The attempt in 1588 by the Spanish Armada to subjugate the Netherlands and England by invading England was defeated, and in 1609, with both sides totally exhausted, fighting was suspended during a 12-year truce made between the new Spanish king and the Dutch Republic. However, attempts to secure a more permanent peace floundered on the question of religious freedom for Catholics in the United Provinces and for Protestants in the southern provinces.

Anxious to prevent a Habsburg presence on its western frontiers, the United Provinces joined with Protestant princes and France against the Habsburg Holy Roman Emperor, Spain, and a coalition of German Catholic states. After the Treaty of Xanten was agreed to on November 12, 1614, the territories were divided between the Catholic Count Palatine of Neuberg and the Protestant Elector of Brandenburg, an arrangement that satisfied neither side and aggravated Protestant and Catholic tensions. Four years later, the whole of Germany was set aflame when Protestants in Bohemia expelled representatives of Emperor Matthias II, who had briefly been governor of the Netherlands in 1578.

The ensuing Thirty Years' War was one of the most horrific conflicts in history, resulting in the deaths of nearly two-thirds of Germany's population, and the Battle of White Mountain in 1620 was the first major battle of that war. The battle was fought mainly due to Holy Roman Emperor Ferdinand II's dealings with the Bohemians and their new king, Frederick of the Palatinate, who Ferdinand regarded as illegitimate.

It's possible the sheer destruction of the conflict would have compelled the armies to modernize anyway, but regardless, the Thirty Years' War devastated the continent, and Germany in particular, in a way that would not be matched until World War I.