With Combat Strength matched only by the Destroyer, powerful torpedoes that can sink enemy ships before they know what's coming, and the ability to launch nuclear weapons, Nuclear Submarines are the scourge of the seas. You'll need Uranium to produce them, but they're well worth the investment - you can use them to pillage coastal districts and improvements to cripple the enemy's infrastructure, or unload your nuclear arsenal on a city and blast through its defenses. Follow the nuclear strike with an attack by a melee or naval melee unit, and you can instantly capture a coastal city if you need to gain a foothold on another continent or hamper an opponent's naval production.
Oh yes, and enjoy their sea-to-land (conventional) missiles when attacking land units on coastal tiles.
Civilopedia entry Edit
The conceptual design of a nuclear-powered submarine was first proposed by the American Naval Research Laboratory in 1939 AD; it was finally realized with the launch of the U.S.S. Nautilus in 1954, which could stay underwater without surfacing for four months … although why one would wish to do so was never explained. Since underwater craft were ideal for launching nuclear-tipped ballistic missiles without warning, it was the perfect Cold War weapon, there not being much other use for such craft. Thus the Soviet Union soon followed the United States in filling the seas with nuclear submarines, beginning with the ill-fated K-19 in 1959. Despite reactor accidents, breakdowns and sinkings, both sides rushed to build ever larger SSBNs. At the height of the Cold War, some five to ten new nuclear submarines were being commissioned each month. Although the pace has slowed somewhat, today six countries deploy nuclear-powered “strategic” submarines (i.e., those meant to kill cities, not other ships): United States, Russia, China, France, United Kingdom and India.