Angst over a potential electromagnetic pulse attack bubbles up every few months, and it\u2019s easy to understand why. The EMP impact envisioned by people who have studied it closely would be downright apocalyptic: a decimated US power grid, and up to 90 percent of Americans dead within a year. It doesn\u2019t help, either, that North Korea recently invoked the specter of an EMP attack, and seems increasingly like it would have the wherewithal to pull one off.