Even though the United States is in the process of reducing the number of warheads deployed on its long-range missiles and bombers, consistent with the terms of the New START Treaty, it also plans to develop new delivery systems for deployment over the next 20-30 years. The 115th Congress will continue to review these programs, and the funding requested for them, during the annual authorization and appropriations process. During the Cold War, the U.S. nuclear arsenal contained many types of delivery vehicles for nuclear weapons. The longer-range systems, which included long-range missiles based on U.S. territory, long-range missiles based on submarines, and heavy bombers that could threaten Soviet targets from their bases in the United States, are known as strategic nuclear delivery vehicles. At the end of the Cold War, in 1991, the United States deployed more than 10,000 warheads on these delivery vehicles. That number has declined to less than 1,500 deployed warheads today, and is slated to be 1,550 deployed warheads in 2018, after the New START Treaty completes implementation. At the present time, the U.S. land-based ballistic missile force (ICBMs) consists of 400 land-based Minuteman III ICBMs, each deployed with one warhead. The fleet has declined to 400 deployed missiles, while retaining 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 can carry up to 24 Trident II (D-5) missiles, although they will carry only 20 under the New START Treaty. The Navy converted 4 of the original 18 Trident submarines to carry non-nuclear cruise missiles. The remaining carry around 1,000 warheads in total; that number will decline as the United States implements the New START Treaty. Nine of the submarines are deployed in the Pacific Ocean and five are in the Atlantic. The Navy 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 Columbia class submarine that will replace the existing fleet beginning in 2031. The U.S. fleet of heavy bombers includes 20 B-2 bombers and 54 nuclear-capable 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-range bomber 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 and the W80 warhead for cruise missiles. The Obama Administration completed a review of the size and structure of the U.S. nuclear force, and a review of U.S. nuclear employment policy, in June 2013. This review has advised the force structure that the United States will deploy under the New START Treaty. It is currently implementing the New START Treaty, with the reductions due to be completed by 2018. The Trump Administration has indicated that it will conduct a new review of the U.S. nuclear force posture and has pledged to continue most, if not all, of the modernization programs. Congress will review the Administration's plans for U.S. strategic nuclear forces during the annual authorization and appropriations process, and as it assesses U.S. plans under New START and the costs of these plans in the current fiscal environment.