1. Peace of Westphalia and the New State System
The Peace of Westphalia (1648) ended the Thirty Years' War and established the modern principle of state sovereignty, in which rulers held recognized authority within fixed, internationally acknowledged borders.
Ended the Thirty Years' War (1618--1648); recognized Dutch and Swiss independence; extended cuius regio, eius religio to Calvinism alongside Lutheranism and Catholicism; weakened the Holy Roman Empire while strengthening France; founded the modern state system based on sovereign equality and non-interference.
Peace of Augsburg (1555, Lutheran/Catholic choice only, within the Holy Roman Empire) vs. Peace of Westphalia (1648, adds Calvinism, ends the Thirty Years' War, establishes the sovereign-state system).
Students assume Westphalia unified Germany; it actually left the Holy Roman Empire fragmented into hundreds of virtually sovereign territories, delaying German unification until 1871.
1648 Westphalia $arrow$ ends 30 Years' War $arrow$ sovereign states $arrow$ HRE stays fragmented.