People like to talk about how the future of warfare will be different, but it has already started to arrive. For some years now, the beginnings of major shifts in the character of warfare have been visible in places like eastern Ukraine and the Middle East. Across these battlefields, rival powers made investments and developed doctrine, providing ample evidence that future wars promise extreme lethality not seen since World War II. The hybrid warfare underway in the Middle East and eastern Europe is a small-scale preview. The next fight will be defined by a violent intensity that will test the U.S. military’s might in the cauldron of battle. As leading scholars and policymakers have discussed, revisionist and increasingly belligerent actors are working to erode the pillars of the global political and economic system that evolved since World War II and reached a high point after the Cold War. In attempting to remake the global order, these actors are developing and employing technologies and tactics that offset America’s military dominance on land, at sea, in the air, and in space and cyberspace.