The Peace of Westphalia (1648) — Birth of the Modern State System

The Thirty Years War (1618–1648)
Europe was devastated by a series of religious and political wars, the most destructive being the Thirty Years' War. This war involved most of the major European powers and killed millions of people — roughly one third of the German population died from war, famine, and disease.

The war was fought over religious differences between Catholics and Protestants, as well as political rivalries between kingdoms and the Holy Roman Empire.

The Peace of Westphalia
In 1648, the warring parties signed the Peace of Westphalia — a series of treaties that ended the Thirty Years War. This is considered the most important event in the history of International Relations because it established the principles of the modern state system.

Key Principles Established by Westphalia

Sovereignty: Each state has supreme authority within its own territory. No outside power — including the Pope or the Emperor — can interfere in a state's internal affairs.

Territorial Integrity: States have the right to control their own territory and borders.

Legal Equality of States: All sovereign states are legally equal, regardless of their size or power.

Non-Interference: States should not interfere in the internal affairs of other states.

These principles became the foundation of international law and diplomacy. Even today, debates about intervention, sovereignty, and human rights are rooted in the Westphalian framework.