The story of the Ohio-Class SSGN.
The Ohio SSGNs’ awesome firepower, however, will only remain in the U.S. Navy for around another decade or so, at which time the entire fleet of Ohio-class submarines will be gradually replaced with the new Columbia-class ballistic-missile submarines. The conventional land-attack role will be taken up by the large fleet of Virginia-class attack submarines, which can be equipped with the Virginia Payload Module to launch up to forty Tomahawks each. While this means it will take four Virginia-class submarines to equal the firepower of a single Ohio-class, it will distribute that firepower more widely across the fleet and will likely prove adequate in most scenarios—short of World War III.
The Ohio-class ballistic-missile submarine (SSBN) was built to destroy cities and military installations in the event of a nuclear war—or more precisely, to deter adversaries from ever starting one. However, following the end of the Cold War, the U.S. Navy determined that it didn’t need all eighteen of its underwater horsemen of the apocalypse for the nuclear deterrence mission.
Recommended: 8 Million People Could Die in a War with North Korea