1966 Soviet submarine global circumnavigation

The 1966 Soviet submarine global circumnavigation (Russian: Подводная кругосветка советских атомоходов), was announced to be the second submerged around-the-world voyage executed by the detachment of the nuclear powered submarines that served in the Soviet Navy. The expedition was an early example of blue-water operations and the power projection of the Soviet Union through its Navy's nuclear-powered submarine fleet, and it paved the way for future operations during the latter half of the Cold War.

Source: Wikipedia — 1966 Soviet submarine global circumnavigation (CC BY-SA 4.0)