What is the background of international cooperation?

Answer 1

In ancient times, people tend to agree with regards to trade and occupation of territories. Thus, alliances existed among early European and Asian countries principally for exchange of goods and protection of their country from superpowers.

Formal international cooperation came about after World War I when countries deemed it right that there should be agreeements with regards to declaration of war. Thus, the UN was born principally for international cooperation.