Religion was thus more than sufficient as a cause of conflict in Europe in the sixteenth and seventeenth centuries. As it happens, however, there was another major cause of conflict, one that lent to the savagery of many of the religious wars of the period: the Little Ice Age. A naturally occurring fluctuation in earth’s climate saw the average temperature drop by a few degrees during the period, enhancing the frequency and severity of bad harvests. In the Northern Hemisphere, that change began in the fourteenth century but became dramatically more pronounced between 1570 and the early 1700s, with the single most severe period lasting from approximately 1600 until 1640, precisely when the most destructive religious war of all raged in Europe, the Thirty Years’ War that devastated the Holy Roman Empire.
Lower temperatures meant that crop yields were lower, outright crop failures more common, and famines more frequent. In societies that were completely dependent on agriculture for their very survival, these conditions ensured that social and political stability was severely undermined. To cite just one example, the price of grain increased by 630% in England over the course of the sixteenth and early seventeenth centuries, driving peasants on the edge of subsistence to even greater desperation. Indeed, historians have now demonstrated that not just Europe, but major states across the world from Ming China, to the Ottoman Empire, to European colonial regimes in the Americas all suffered civil wars, invasions, or religious conflicts at this time, and that climate was a major causal factor. Historians now refer to a “general crisis of the seventeenth century” in addressing this phenomenon.
Thus, religious conflict overlapped with economic crisis, with the latter making the former even more desperate and bloody. The results are reflected in some simple statistics: from 1500 to 1700, some part of Europe was at war 90% of the time. There were only four years of peace in the entire seventeenth century. The single most powerful dynasty, the Habsburgs, were at war two-thirds of the time during this period.