Final answer:
The Treaty of Westphalia was significant for international relations as it established state sovereignty and the nation-state system, ended wars, and introduced the principle of non-interference in internal affairs.
Step-by-step explanation:
The Treaty of Westphalia, signed in 1648, was significant for international relations as it marked a turning point in the concept of state sovereignty and the establishment of the nation-state system.
It ended the Thirty Years' War and the Eighty Years' War, bringing stability and territorial boundaries to Europe.
The treaty recognized the principle of cuius regio, eius religio, which allowed rulers to determine the religion of their own territories.
This concept laid the foundation for the principle of non-interference in the internal affairs of other sovereign states, a fundamental aspect of international relations.