Since at least 2016, diplomats, spies and military officers have suffered from unexplained brain injuries likely caused by a microwave weapon used by a foreign adversary, although sources say the U.S.

The miniaturized microwave device was allegedly secretly purchased from a complex Russian criminal network for about $15 million in a Pentagon-funded operation.

For years, the U.S. government has doubted the stories of those suffering from AHI, commonly called Havana Syndrome. Now, ...