With reference to the situation in the empire, outline the chief causes of the Thirty Years War.
The religious and constitutional struggle of the Thirty Years War was one of the longest and most destructive conflicts in modern history. The period leading up to the war was characterised simultaneously by an extreme piety and increasing confessional divide in the empire, yet in its numerous theological, political and legal forms, the confessional conflict alone cannot be considered the sole cause of the conflagration. A myriad of structural factors led to the disabling and ultimately destructive breakdown of the Imperial constitution by 1618. Socio-economic considerations and various political factors are emphasised to varying degrees by historians from differing backgrounds and schools of thought. The historiographical debate identifies several potential groups to blame in causing the crisis, highlighting either the rivalry between the territorial princes for dominance in the Empire, or the continuous power struggle between the princes and the Emperor. The outbreak of war must also be seen within the political context of European power politics, as the Habsburgs and Bourbons struggled for supremacy on the continent, whilst the Protestants represented an increasingly powerful bloc in northern Europe, threatening the status quo of Habsburg peripheral empires. The precarious balance of power was maintained only by the antiquated structures of the Holy Roman Empire. Under severe internal and external strain, it merely required a final spark, which it found in Bohemia.
Long-term causes of the war may be ascribed to the growing social, economic and religious instability during the sixteenth century. In this period, Germany enjoyed relative stability, whilst neighbouring France was beleaguered by the war of religion from 1562 to 1598. Yet Hughes argues this façade of stability is deceptive, pointing out its proximity to the Thirty Years War. It is sometimes argued this was a period of German economic decline, which may have exacerbated religious tensions, however it was merely a period of economic change, as cities began to experience decline and trade shifted away from the Hanseatic league. Nevertheless, there was a definite increase in pauperism and vagabondage in the years running up to 1618, as well as a sharp increase in criminality between 1560 and 1600, demonstrated by the growth of robber gangs. Ultimately, the wave of peasant revolts between the 1580s and 1620s was indicative of deep social and political tensions, which Hughes argues could be exploited for political ends, as religious tension coincided with the revival of social problems.
 Michael Hughes, Early Modern Germany, 1477 – 1806 (Philadelphia: University of Pennsylvania Press, 1992), p. 61
 Ibid, p. 11
 Ibid, p. 76