Reimagining Nuclear Arms Control

A renewed U.S.-Russian nuclear arms race, which has been largely qualitative so far but could soon turn quantitative, is underway. To compensate for perceived conventional inferiority, Russia maintains a much larger force of nonstrategic nuclear weapons (NSNWs) than the United States does, is fielding new systems, and may be increasing its overall number of nonstrategic warheads. In response, the United States is developing and deploying its own new types of NSNWs. (Russia and the United States generally use the term “strategic” to describe nuclear weapons with sufficient range to reach the other’s homeland from deployment locations in the possessor’s homeland or, in the case of sea-launched ballistic missiles, from firing locations well away from the other’s coast.) 

At the strategic level, Russia believes that the United States is seeking capabilities—including high-precision conventional weapons and ballistic missile defenses—to undermine its nuclear deterrent. Moscow’s response has included the development and deployment of various new kinds of strategic weapons. The 2010 New Strategic Arms Reduction Treaty 2 REIMAGINING NUCLEAR ARMS CONTROL: A COMPREHENSIVE APPROACH (New START) helps to manage this competition by limiting all currently deployed U.S. and Russian strategic weapons, though it will expire in 2026. 
Like Russia, China believes that the United States seeks to undermine its nuclear deterrent. As a result, Beijing is improving and expanding its long-range nuclear forces without giving any indication of its intended endpoint. Separately, it is also modernizing and enlarging its force of regional missiles, including dual-use weapons, in a likely effort to acquire more credible options for limited nuclear use. (Dual-use weapons can accommodate a nuclear or nonnuclear warhead.)

Here