America must defend our digital infrastructure, here and overseas, to win the next war

For most of American history, national defense has been understood geographically. There was American territory and foreign territory, borders to defend, military installations to protect and American forces stationed around the world. Even as warfare evolved, the basic concept remained relatively simple: the United States had physical assets that needed protection from foreign adversaries.

Technology has fundamentally changed that calculation. Today, some of the most important assets supporting America's economy...