對馬海峽
On 5 January 1968, "Pueblo" left the U.S. Navy base at Yokosuka, Japan, in transit to the U.S. naval base at Sasebo, Japan; from there she left on 11 January 1968, headed northward through the Tsushima Strait into the Sea of Japan. She left with specific orders to intercept and conduct surveillance of Soviet Navy activity in the Tsushima Strait and to gather signal and electronic intelligence from North Korea. The declassified SIGAD for the National Security Agency (NSA) Direct Support Unit (DSU) from the Naval Security Group (NSG) on "Pueblo" during the patrol involved in the incident was USN-467Y. AGER (Auxiliary General Environmental Research) denoted a joint Naval and National Security Agency (NSA) program.