Answer:
The Treaty of Versailles
Explanation:
Following World War I, nations worked together to ensure that such would never happen again.
One significant agreement showing this is the Treaty of Versailles, which was signed in 1919 at the Paris Peace Conference.
The Treaty essentially outlined the terms of peace and established the League of Nations that would aim to begin an era of international cooperation.
Although ultimately unsuccessful, the league did show the desire for countries to prevent wars in the future.
