The story of U.S. personnel who came down with hearing loss and other symptoms after serving in Cuba continues to get stranger. Most of the two dozen injured Americans claim they heard a high-pitched buzzing which was localized, like a beam they could walk into or away from. Some of the injured suffered permanent hearing damage and even mild brain damage. Today, Politico reports something like this has happened before, back when the USSR targeted U.S. spies in Moscow and Havana during the Cold War:

Two intelligence officials tell POLITICO they’re confident that the attacks were conducted with an “energy directed” or “acoustic” device, possibly similar to one used by Soviet intelligence in Havana more than four decades ago, but remain unsure of its exact nature…

Of particular interest to federal officials is the former Soviet technique of using radio waves, like microwaves, to target U.S. signals collection in Moscow. In the 1970s, amid escalating spy tensions between the United States and Russia, the Soviets targeted the U.S. embassy in Moscow with radio microwaves in an effort to disrupt U.S. radio surveillance of Russian interests in post Cold-War Moscow, according to multiple Cold War-era recountings. The incident, known as the “Moscow Signal,” was never formally solved — after the U.S. embassy installed screens in its compound, the issue went away.

The use of energy waves or sound as weapons can be a particularly nasty form of covert attack. Not always audible to the human ear, the mysterious devices have surfaced in rumors periodically in Cold War spy history. Answers have remained as ambiguous. As far back as the 1970s Moscow Signal incident, medical professionals suspected the use of such mysterious weapons could lead to brain damage, blood disorders and hearing impairments in exposed personnel — symptoms nearly identical to what targeted U.S. officials are experiencing now.

The idea that Cuba had invented some never-before-seen sonic weapon always seemed like a stretch, given the general impoverishment of the island. It’s much more believable that this is a recycling of 40-year-old techniques pioneered by the Soviets.

This article from Science magazine in 1979 gives an overview of the Moscow Signal and the U.S. response, which included secretly testing people who had been exposed to it for genetic damage. For most of the time it was aimed at U.S. personnel the power of the signal was very weak and a study by Johns Hopkins later concluded it had created no substantial health problems. However, there were a couple years in the late 1970s when the power of the signal was much higher. The AP reported in May 1979 when the signal was finally cut off:

For the last three and a half years, strong beams have been aimed at the embassy’s upper floors from transmitters east and south of the 10‐story structure.

“Neither the east nor the south signal has operated since the end of April,” the embassy spokesman said. “Hence, we have detected no radiation since that time from those sources.”

Other microwave sources in the area have been detected for years but were not considered comparable to the searchlight‐like beams aimed at the embassy building.

But why attack the U.S. (and Canada) after the U.S. normalized relations with Cuba? Isn’t that counterproductive? When this story first broke the claim was that Raul Castro was genuinely surprised this had happened, even offering to allow the FBI to come to Cuba to investigate. A former intelligence official tells Politico that may point to a rogue faction of hard-liners in Cuba looking to sabotage the relationship with the U.S.

If the attacks are indeed the work of a renegade Cuban intelligence faction, the former U.S. intelligence official said, that might be a sign that Cuban President Raúl Castro’s grip on power — he succeeded his brother, Fidel, as president in 2008 — may not be as strong as many outsiders assume.

Again, the idea that these are older hardliners within Cuba fits with the idea of using 40-year-old tech to attack the U.S. This could be Cuban spies who remember the glory days of the Cold War and are looking to bring it back. And the fact that a dictator like Raul Castro can’t identify who is responsible for the attack does suggest he’s not as powerful as his brother Fidel once was.