The economic catastrophes afflicting the United States and the world in the first half of the twentieth century can be divided into several phases but historians generally see connections between them and their shared origins in the cataclysm of World War I. The crisis of 1914–18 brought an end to the intense and deepening late nineteenth-century networks of global trade and, following the peace treaties, economic and other kinds of nationalism flourished. In particular, the United States adopted policies restricting immigration and trade that were especially ill-suited to its new, postwar position as the world’s great lender, manufacturer, and consumer.