"De Jure Belli ac Pacis," written by Hugo Grotius in 1625, is a foundational text in international law. It discusses the principles of just war and peace, outlining the legal and moral frameworks that govern conflicts between nations. Grotius argues that wars can be justified under certain conditions and emphasizes the importance of treaties and diplomacy in maintaining peace. The work is significant for establishing the idea that laws of war should be based on reason and justice rather than mere power. It influenced later legal scholars and contributed to the development of modern concepts of sovereignty and human rights, shaping international relations to this day.