How did the Thirty Years’ War influence Hugo Grotius’s writing?

The Thirty Years’ War, which began in 1618, profoundly influenced Hugo Grotius’s seminal work, De Jure Belli ac Pacis (On the Law of War and Peace), published in 1625. Observing a widespread lack of restraint in warfare across the Christian world—behavior he deemed shameful even for "barbarous nations"—Grotius was driven by a practical objective to minimize bloodshed.12

To address this violence, he sought to establish a general theory of law (jurisprudentia) capable of regulating conflicts between independent powers. He argued for a common law among nations that remained valid both during and in the conduct of war. By placing natural law at the center of his work, he aimed to create a framework that could transcend religious divisions, though he also incorporated religious norms and arguments based on utility to ensure his goal of limiting violence was as effective as possible. Ultimately, his work laid a foundational contribution to the development of international law.213