ON THIS DAY: 4 August 1945 – One of the most ingenious espionage devices ever created, known simply as ‘The Thing’, was presented to the American ambassador in Moscow, hidden inside a beautifully carved wooden plaque of the Great Seal of the United States.
The plaque was presented to W. Averell Harriman at the American ambassador’s residence, Spaso House, by a group of Soviet schoolchildren as a gesture of friendship. It appeared to be nothing more than an impressive hand-carved wooden plaque, and embassy staff proudly hung it on the wall behind the ambassador’s desk, where it remained for years.
The timing was significant. Germany had surrendered just three months earlier, but relations between the Soviet Union and its Western allies were already beginning to deteriorate, marking the start of what would become the Cold War.
Hidden inside the plaque was a revolutionary listening device. Unlike conventional bugs of the era, The Thing contained no batteries, no wires and no power supply.
It had been designed by the brilliant Soviet inventor Leon Theremin, best known for inventing the electronic musical instrument that bears his name.
The device consisted of a tiny metal cavity connected to a thin antenna. On its own, it was completely inactive and emitted no signal, making it virtually impossible to detect with the technology of the day. It had no active transmitter and only operated when illuminated by an external radio beam, remaining completely silent until activated.
Soviet intelligence officers, positioned in a nearby building or van, directed a powerful radio signal at the embassy. The incoming radio waves energised the hidden device, while vibrations caused by voices inside the ambassador’s office altered the reflected signal. The returning transmission could then be received and converted back into sound.
Known today as a passive resonant cavity microphone, the technology was decades ahead of its time.
The device remained undetected until 1952. According to most accounts, British radio operators accidentally overheard conversations from the embassy on an open Soviet radio frequency, prompting an intensive security search by American officials. Eventually, the ingenious device was discovered concealed within the plaque.
Security experts were astonished by its sophistication. Even today, The Thing is regarded as one of the greatest technical achievements in the history of espionage.
It is an extraordinary reminder that one of history’s most successful spying operations began not with a break-in or a hidden camera, but with a seemingly innocent diplomatic gift.