- Common abilities:
The Nuclear Submarine is tougher and stronger than the Modern-era model, with engines and battle systems updated for the Information Era. It too is invisible to most units and can see other submarines. Most importantly, Nuclear Submarines can carry Guided Missiles and Nuclear Missiles, making them one of the most dangerous weapons in the game. This ensures their use in a naval invasion, destroying defending units and cities alike, after which they can be used as long range defenders, ensuring troops may be transported to the battlefield without being harassed by naval warships.
Nuclear submarines are Cold War-era vessels, designed to stealthily carry large numbers of nuclear missiles under the ocean for extended voyages. These huge vessels are nuclear powered themselves, giving them an almost unlimited cruising range (or as long as the food holds out). Nuclear submarines are strategic weapons platforms. They carry intercontinental missiles, able to fly halfway around the world before hitting their target - generally an enemy city. While they may carry torpedoes and surface-to-air missiles for their own defense, their primary duty is to stay hidden and avoid direct conflict with the enemy. They must survive at all costs.
Nuclear submarines formed a part of the US' and USSR's "Mutual Assured Destruction" doctrine: if either side were to hit the other with a sneak nuclear attack, no matter how successful the attack, if even one enemy sub survived it could rain down a horrifying amount of death upon the victor, destroying them as well. Thus, the doctrine states, unless one can be TOTALLY assured that they can absolutely and without question destroy every one of the enemy's nuclear subs, planes and ICBMs, nuclear war is unwinnable. Whether one believes the M.A.D. doctrine to be insane or not, there has been no nuclear war on this planet since it was implemented.