The Old Swiss Confederacy a "de facto" independent state throughout the early modern period, although still nominally part of the Holy Roman Empire until 1648 when the Treaty of Westphalia ended the Thirty Years' War. The Swiss Reformation divided the confederates into Reformed and Catholic parties, resulting in internal conflict from the 16th to the 18th centuries; as a result, the federal diet () was often paralysed by hostility between the factions. The Swiss Confederacy fell to invasion by the French Revolutionary Army in 1798, after which it became the short-lived Helvetic Republic. The adjective "old" was introduced after the Napoleonic era with ,
Peace of Westphalia European issues of the time. Scholars of international relations have identified the Peace of Westphalia as the origin of principles crucial to modern international relations, including the inviolability of borders and non-interference in the domestic affairs of sovereign states. This system became known in the literature as Westphalian sovereignty. Although scholars have challenged the association with the Peace of Westphalia, the debate is still structured around the concept of Westphalian sovereignty. Peace of Westphalia The Peace of Westphalia () was a series of peace treaties signed between May and October 1648 in the Westphalian cities of Osnabrück and Münster, largely