Map of Soviet sleeper cells, 1968
The Soviet sleeper cell program was a top secret program undertaken by the intelligence services of the Soviet Union during the Cold War. The program, an integral part of Project Nova, saw the Soviet government position hundreds of American communist sleeper agents in every US state capital with Nova 6 bombs, and the Soviets communicated with the sleeper cells by broadcasting number transmissions from a numbers station in the Gulf of Mexico. In the event of a war with the United States, the USSR could send encrypted messages to its sleeper cells and have them kill their own countrymen by releasing toxic Nova 6 gas in the major cities of America, which would be a devastating blow to the US. The CIA gathered intelligence on the program and launched an operation to destroy the numbers station, resulting in the Rusalka crisis of 1968. With the Rusalka destroyed, the Soviet sleeper cells lost touch with the government, and Project Nova was derailed. In 1981, the Soviet spymaster "Perseus" attempted to reactivate the sleeper cells as part of his plot to turn America's "Operation Greenlight" nuclear bomb contingency program against it, but the CIA assassinated his lieutenant Robert Aldrich in New Mexico and discovered the identities of his sleeper agents, whom they neutralized.