The US military and intelligence communities have spent much of the last two decades fighting wars in which the US significantly over-matched its opponents technologically—on the battlefield and off. In addition to its massive pure military advantage, the US also had more sophisticated electronic warfare and cyber capabilities than its adversaries. But those advantages haven’t always translated into dominance over the enemy. And the US military is facing a future in which American forces in the field will face adversaries that can go toe to toe with the US in the electromagnetic domain—with disastrous physical results.