Fighting right up to the line that would clearly trigger a Western response is known as “grey zone conflict,” says Bryan Clark, a senior fellow at the Center for Strategic and Budgetary Assessments, a defense think tank that has run several war games with Eastern European nations. “They’re doing a very good job of playing at the edges,” he says of the Russians. Because an obvious U.S. military response may not be considered desirable in such circumstances, there is a premium now on developing U.S. systems that can ght as surreptitiously as Russia does, by disrupting their military command and control with electronic warfare and cyberattacks, Clark says…So the Pentagon is investing more in ground-based missile systems with names such as the Long Range Precision Fires and the Multi-Mission Launcher that are not as easily detected as aircraft and can get closer to enemy targets, Clark says. The propensity of Putin to fight right up to the line that could trigger U.S. military involvement and the way Russia’s long- range air defenses are keeping U.S. forces at bay “are the two big military challenges the U.S. is just now coming to grips with,” Clark says.