The United States has more than 148,000 public water systems, many of them small and resource-constrained. Rather, a foreign adversary does not need to defeat the U.S. military in order to impose costs on American society. This is why the simplest test of the Iran war is not whether the United States can continue striking Iran. Does the United States have more, rather than less, capacity to deal with the next crisis? The recent attacks on water systems are a warning precisely because their effects were limited.