This work by the Dutch jurist and statesman Hugo Grotius formulated the basic principles of modern international law, especially as it relates to war. Grotius believed that nations are bound by natural law based on human nature. His views significantly influenced Jefferson’s concept of the law of nations, including the validity of treaties when an alliance has grown dangerous or disagreeable. Jefferson cited Grotius in a 1793 memo he wrote as secretary of state in which he argued that the United States had an obligation to honor treaties made with France before the French Revolution changed its government.