The Ohio class of nuclear-powered submarines is the sole class of ballistic missile submarines (SSBN) currently in service with the United States Navy. Fourteen of the eighteen boats are SSBNs, which, along with U.S. Air Force strategic bombers and intercontinental ballistic missiles, constitute the nuclear-deterrent triad of the U.S. The remaining four have been converted from their initial roles as SSBNs to cruise missile submarines (SSGNs). The Ohio-class boats, each displacing 18,750 tons submerged, are the third largest submarines in the world, behind the 48,000-ton Typhoon class and 24,000-ton Borei class of the Russian Navy. The Ohio class replaced the Benjamin Franklin- and Lafayette-class SSBNs. The lead submarine of this class is the USS Ohio. The 14 Trident II SSBNs together carry about half of U.S. active strategic thermonuclear warheads. Although the Trident missiles have no preset targets when the submarines go on patrol, they can be given targets quickly, from the United States Strategic Command based in Nebraska, using secure and constant radio communications links, including very low frequency systems. All the Ohio-class submarines, except for USS Henry M. Jackson, are named for U.S. states, which U.S. Navy tradition had previously reserved for battleships and cruisers. The Ohio-class boats are the largest submarines ever built for the U.S. Navy. Two Russian Navy classes have larger total displacements: the Soviet-designed Typhoon-class submarines have over twice the total displacement, and Russia's Borei-class submarines have roughly 25% greater displacement, but the Ohio-class boats carry more missiles than either: 24 Trident missiles apiece, versus 16 by the Borei class (20 by the Borei II) and 20 by the Typhoon class.
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