Since the end of the Cold War, the United States and other Western powers have pursued a noble idea — that by tying themselves economically to their rivals, they might escape the dismal cycle of great-power conflicts. In that spirit, Germany encouraged gas and oil imports from Russia over the last decade even as Vladimir Putin was stepping up his aggression against neighboring states. Europe and the United States embraced trade with China, expanding ties as the Asian nation became the world’s largest exporter, including some critical goods. For several decades, Western powers seemed satisfied that, in the words of the German philosopher Immanuel Kant, the “power of money … perhaps the most dependable of all powers,” would compel nations “to prevent war wherever it threatens to break out.”