WASHINGTON—In 2019, a group of Americans was observing the cellphone signals coming from military sites across Eastern Europe. At one of the locations, the Nyonoksa Missile Test Site in northern Russia, the group identified 48 mobile devices present on Aug. 9, one day after a mysterious radiation spike there generated international headlines and widespread speculation that a Russian missile test had gone wrong.

Source: Wall Street Journal July 18, 2020 12:00 UTC