From the Chewy Cold War

In 1968, Yankee class Soviet subs (Project 667) were the first with firepower comparable to their American SSBN counterparts. The longest Cold War trailing operation of a Soviet boomer conducted by a US submarine (up until that time) was completed successfully ten years later.

The USS Batfish (SSN-681) trailed a Yankee for 44 continuous days, as part of an operation code named Evening Star, begun 17 March 1978 after Batfish intercepted the Yankee in the Norwegian Sea. When Batfish lost contact during a severe storm on March 19th, a Navy P-3 Orion patrol aircraft was sent from Reykjavik, Iceland to reestablish firm contact.

Batfish, towing a 1,100-foot sonar array, had earlier been dispatced from Norfolk to intercept this SSBN. U.S. intelligence had been alerted to her probable departure from the Kola Peninsula by CIA-sponsored intelligence activities and U.S. spy satellites.

_____________________________________________________________ Various tellings of the tale leave holes. Stuff gets redacted, you know. On rainy days, it is sometimes fun to identify and consider inconsistencies. As readers know, submarines are always silent and strange. Here, careful readers may find several examples of inconsistencies from Wikipedia source:

On 2 March 1978, Batfish, commanded by Commander Thomas Evans (who retired as a Rear Admiral), left Charleston, South Carolina, on what would transpire to be a remarkable 77-day patrol known as "Operation Evening Star." On 17 March, Batfish detected a Navaga-class ballistic missile submarine (NATO reporting name "Yankee I") of the Soviet Navy at the north end of the Norwegian Sea some 200 miles (300 km) above the Arctic Circle. She began trailing the Yankee, collecting valuable information on how the Soviets operated. During the next 50 days, the Yankee never detected Batfish, and Batfish lost the Yankee only twice: once was during a bad storm, and once when a fishing fleet passed overhead. Both times the Soviet boat was quickly reacquired. The Soviets remained unaware that their boat had been followed until Warrant Officer John Anthony Walker sold them the information. (Walker pleaded guilty to espionage in 1985.)