International law is derived primarily from two sources: international agreements and customary international practice. The Yalta Conference took place in a Russian resort town in the Crimea from February 4–11, 1945, during World War Two.Franklin ultimately helped negotiate a cessation of hostilities and a peace treaty that officially ended the Revolutionary War. Discover! City of Philadelphia. President Franklin Delano Roosevelt took office determined to improve relations with the nations of Central and South America. Roosevelt scored his greatest foreign policy success through his "good neighbor" policy towards Latin America and countries of the Western Hemisphere. International law is derived from two primary sourcesinternational agreements and customary practice. The Yalta Conference took place in a Russian resort town in the Crimea from February 4–11, 1945, during World War Two. At Yalta, U.S. President Franklin D. International agreements are formal commitments between countries, categorized as bilateral or multilateral.