Israel’s Iron Dome relies on the ancient Chinese principle of wu wei — or doing nothing:
Iron Dome uses two radars to quickly calculate the trajectory of the incoming rocket and do nothing if the rocket trajectory indicates it is going to land in an uninhabited area. But if the computers predict a rocket coming down in an inhabited area, guided missiles are fired to intercept the rocket. This makes the system cost-effective. That’s because Hezbollah fired 4,000 rockets in 2006, and Palestinian terrorists in Gaza have fired over six thousand rockets in the past eight years and the Israelis know where each of them landed. Over 90 percent of these rockets landed in uninhabited areas and few of those that did hit inhabited areas caused casualties.