A recent story from Florida should direct policymakers’ attention to a glaring strategic problem in American defense. In the city of Oldsmar, a small community in the Tampa metro area, an unknown hacker gained access to the chemical controls of the municipal water treatment system. Fortunately, an operator at the facility observed the breach in real time, watching as the intruder set the level of sodium hydroxide, commonly known as lye, to 100 times its normal level. The operator was able to immediately undo the change, so no one was harmed. But what if that instant detection hadn’t happened? As...