The Treaty of Westphalia: 1648

The Treaty of Westphalia was a collective name given to a series of peace agreements that brought about an end to the bloody Thirty Years War (1618-48) in Europe. The peace made at Westphalia would cement the Nation-State as the primary focus of the International Relations discipline. The treaty was devised at the first modern diplomatic congress and placed emphasis on the sovereign state governed by a sovereign ruler. 

The Peace of Westphalia, 1648. The Treaty recognized the new boundaries of European States, including an independent Portugal and a Unified Netherlands.