CRS – U.S. Strategic Nuclear Forces: Background, Developments, and Issues, updated November 3, 2015.

“Even though the United States plans to reduce the number of warheads deployed on its long-range missiles and bombers, consistent with the terms of the New START Treaty, it also plans todevelop new delivery systems for deployment over the next 20-30 years. The 114th Congress will continue to review these programs, and the funding requested for them, during the annual authorization and appropriations process…At the present time, the U.S. land-based ballistic missile force (ICBMs) consists of 450 Minuteman III ICBMs, each deployed with one warhead. The fleet will decline to 400 deployed missiles, while retaining all 450 launchers, to meet the terms of the New START Treaty. The Air Force is also modernizing the Minuteman missiles, replacing and upgrading their rocket motors, guidance systems, and other components, so that they can remain in the force through 2030. It plans to replace the missiles with a new Ground-based Strategic Deterrent around 2030. The U.S. ballistic missile submarine fleet currently consists of 14 Trident submarines; each carries 24 Trident II (D -5) missiles. The Navy converted 4 of the original 18 Trident submarines to carry non-nuclear cruise missiles. The remaining carry around1,000 warheads in total; that number will decline as the United States implements the New START Treaty . The Navy has shifted the basing of the submarines, so that nine are deployed in the Pacific Ocean and five are in the Atlantic, to better cover targets in and around Asia. It also has undertaken efforts to extend the life of the missiles and warheads so that they and the submarines can remain in the fleet past 2020 . It is designing a new submarine and will replace the existing fleet beginning in 2031. The U.S. fleet of heavy bombers includes 20 B-2 bombers and 76 B-52 bombers. The B-1 bomber is no longer equipped for nuclear missions. The fleet will decline to around 60 aircraft in coming years, as the United States implements New START . The Air Force has also begun to retire the nuclear-armed cruise missiles carried by B-52 bombers, leaving only about half the B-52 fleet equipped to carry nuclear weapons. The Air Force plans to procure both a new long-rangebomber and a new cruise missile during the 2020s. DOE is also modifying and extending the life of the B61 bomb carried on B-2 bombers and fighter aircraft…”