START Treaties and Ballistic Missiles: A Strategic Overview

Strategic ballistic missiles have long formed the core of U.S. and Russian nuclear deterrence. The START treaties and ballistic missiles are therefore closely linked, as these agreements established limits on warheads, launchers, and delivery systems designed to reduce the risk of nuclear escalation.

From START I to New START, arms-control arrangements combined numerical restrictions with inspections, notifications, and data exchanges. Their provisions influenced how strategic missile forces were deployed, modernized, reduced, and verified throughout the post–Cold War era.

How START Treaties Regulate Strategic Ballistic Missiles

START treaties and ballistic missiles regulate strategic nuclear forces by setting limits on delivery vehicles, deployed warheads, and, in some agreements, associated launchers. Their primary purpose is to prevent either the United States or Russia from maintaining an unconstrained strategic arsenal.

These agreements define which intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers count toward treaty ceilings. They also establish rules for counting warheads, distinguishing deployed systems from reserve or nondeployed equipment.

Compliance depends on detailed verification provisions rather than declarations alone. Data exchanges, notifications, inspections, national technical means, and the exchange of information about missile facilities help each party monitor treaty obligations.

The treaties also regulate how strategic ballistic missiles may be tested, deployed, eliminated, or converted. As a result, they influence force structure and modernization decisions while reducing uncertainty about the size and status of the participating states’ nuclear forces.

START I and the First Limits on U.S. and Soviet Ballistic Missiles

START I was signed by the United States and the Soviet Union in 1991 and entered into force in 1994 after the dissolution of the Soviet Union. It established the first comprehensive, legally binding limits on the two powers’ strategic nuclear forces.

The treaty restricted deployed intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and the warheads assigned to them. Each side was permitted no more than 6,000 accountable nuclear warheads and 1,600 strategic delivery vehicles, subject to detailed counting rules.

START I also addressed missile characteristics, including restrictions on new systems and limits on certain methods of increasing warhead capacity. These provisions influenced how both countries deployed, modified, and retired strategic ballistic missiles.

Verification relied on extensive data exchanges, notifications, inspections, and national technical means such as satellite imagery. Together, these measures enabled each party to monitor compliance and reduced uncertainty surrounding U.S. and Soviet ballistic missile forces.

Warhead and Delivery-Vehicle Restrictions

START I imposed limits on both nuclear warheads and the delivery vehicles capable of carrying them. The treaty established an aggregate ceiling of 6,000 accountable warheads and 1,600 strategic delivery vehicles for the United States and Soviet Union.

Delivery vehicles included intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers. Counting rules assigned specific warhead numbers to each missile type, even when a system carried fewer warheads operationally, creating a standardized basis for verification.

The agreement also restricted the number of warheads that could be attributed to individual missile systems. Multiple independently targetable reentry vehicles (MIRVs) received particular attention because they allow one ballistic missile to deliver several nuclear warheads against separate targets.

These limits affected force planning by requiring reductions, dismantlement, or modification of eligible systems. The restrictions applied to strategic nuclear forces rather than shorter-range missiles, conventional ballistic missiles, or every weapon capable of reaching another country.

Verification Measures and Data Exchanges

Verification relied on several mutually reinforcing tools. National technical means, including satellites and other remote-sensing systems, supported monitoring of declared facilities and missile activity. The treaties also established on-site inspections, allowing inspectors to examine equipment, records, and procedures under agreed rules.

The United States and Soviet Union exchanged detailed notifications about missile deployments, production, movements, tests, and eliminations. These data exchanges helped each side maintain current records of strategic forces and identify changes that might require clarification.

Inspections and notifications were subject to strict timelines and procedures designed to protect sensitive information while confirming treaty compliance. Measures such as perimeter monitoring and inspections at conversion or elimination sites provided evidence that restricted ballistic missiles were not retained in prohibited configurations.

Together, these arrangements made the START treaties and ballistic missiles framework more transparent and predictable. Verification did not depend on a single source of information; it combined national monitoring, shared data, and direct access to declared locations.

START II and Proposed Limits on Multiple-Warhead Missiles

START II was signed by the United States and Russia in 1993 and sought deeper reductions in strategic nuclear forces than START I. Its central provision required the elimination of land-based intercontinental ballistic missiles (ICBMs) equipped with multiple independently targetable reentry vehicles, or MIRVs.

MIRV-equipped missiles can deliver several nuclear warheads against separate targets, increasing destructive capacity without requiring additional launchers. By targeting this capability, START II aimed to reduce the risk of a rapid, highly concentrated first strike and encourage smaller, less destabilizing arsenals.

The treaty also established limits on deployed strategic delivery systems and warheads, with implementation scheduled in stages. However, START II never entered into force. The United States ratified it in 1996, while Russia’s ratification in 2000 was conditional on continued U.S. participation in the Anti-Ballistic Missile Treaty.

Russia withdrew from its START II commitments after the United States left the ABM Treaty in 2002. Consequently, the proposed restrictions on MIRV-equipped ballistic missiles were not implemented, although they influenced later discussions about strategic force reductions.

New START and Modern Strategic Ballistic Missile Forces

New START, signed by the United States and Russia in 2010, limited each country to 700 deployed strategic delivery vehicles and 1,550 deployed strategic warheads. Its scope included intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers.

The treaty supported transparency through data exchanges, notifications, on-site inspections, and procedures for monitoring treaty-relevant facilities. These measures helped each side assess the size and composition of the other’s modern strategic ballistic missile forces.

Under New START, covered systems included:

• Land-based ICBMs and their launchers
• SLBMs deployed on ballistic-missile submarines
• Warheads attributed to deployed missiles
• Heavy bombers equipped for nuclear missions

The treaty did not prohibit modernization. Instead, it established numerical limits while allowing replacement of aging missiles, submarines, and bombers, provided the resulting force remained compliant. New START expired on February 5, 2026, after Russia suspended participation in 2023 and the United States reported limited treaty implementation.

Ballistic Missile Categories Covered by the START Framework

The START treaties primarily covered intercontinental ballistic missiles (ICBMs), defined as land-based ballistic missiles capable of reaching targets at least 5,500 kilometers away. These systems formed the central category in limits on launchers, deployed missiles, and associated warheads.

The agreements also regulated submarine-launched ballistic missiles (SLBMs), which are deployed aboard ballistic-missile submarines. Their launchers and assigned warheads counted toward strategic ceilings, alongside ICBMs, although the treaties applied different technical rules to each system.

Heavy ICBMs received specific treatment because of their payload capacity and multiple-warhead potential. Soviet SS-18 missiles were a prominent example. START I imposed distinct limits on heavy ICBMs, while START II sought to eliminate deployed multiple independently targetable reentry vehicles (MIRVs) on land-based missiles.

The START framework generally focused on strategic ballistic missiles and their launchers, rather than shorter-range or purely tactical systems. Air-launched cruise missiles and heavy bombers were also addressed as strategic delivery systems, but they belonged to separate categories rather than ballistic missiles.

How START Treaties Affect Ballistic Missile Modernization

START treaties and ballistic missiles shaped modernization by linking new deployments to limits on launchers, warheads, and delivery systems. The agreements encouraged the United States and Soviet Union, and later Russia, to replace aging missiles within negotiated force ceilings rather than expand strategic arsenals without restriction.

Treaty compliance influenced force-structure decisions, including the number of deployed intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and associated launchers. Modernization programs therefore required careful accounting, notifications, inspections, and adherence to rules governing testing, deployment, and conversion.

The agreements also established procedures for eliminating or converting systems. Under START I, certain launchers and missiles had to be destroyed or rendered incapable of rapid redeployment. These requirements affected retirement schedules and limited how older systems could be modified while preserving treaty compliance.

New START permitted modernization but capped deployed strategic warheads and delivery vehicles. As a result, modernization generally focused on replacing aging platforms, improving reliability, and maintaining survivability, rather than simply increasing force size. Its limits expired in 2026, leaving future modernization rules dependent on subsequent arms-control arrangements.

Treaty Compliance and Force-Structure Decisions

Treaty compliance shaped how the United States and Russia planned, deployed, and modified strategic ballistic missile forces. Limits on launchers, deployed missiles, and accountable warheads required each side to match modernization programs with treaty ceilings and counting rules.

Force-structure decisions commonly involved:

• Retiring older missiles before deploying replacements
• Adjusting submarine and bomber deployments
• Removing or converting systems that exceeded permitted totals
• Maintaining records for inspections and notifications

Under New START, compliance relied on data exchanges, inspections, notifications, and agreed counting procedures. These mechanisms encouraged predictable force planning while allowing each country to replace aging intercontinental ballistic missiles and submarine-launched ballistic missiles within established limits.

Treaty obligations also influenced the pace and configuration of modernization. A system could be technically operational yet require changes to its deployment status, launcher allocation, or warhead loading to remain compliant. When treaty provisions expired or became inactive, those constraints no longer operated in the same way.

Replacement, Elimination, and Conversion of Missile Systems

Under the START treaties and ballistic missiles framework, replacement programs were permitted when they remained within agreed limits on deployed launchers, warheads, and delivery vehicles. A new missile could enter service as an older system was retired, helping each party modernize without expanding its strategic arsenal.

Elimination required verifiable removal of covered missiles and launchers from operational status. Methods included destruction, disabling, or dismantling, depending on the treaty and equipment involved. These procedures reduced uncertainty and supported inspections and data exchanges.

Conversion allowed certain launchers or facilities to be altered for nonstrategic purposes, where treaty rules permitted it. Typical compliance measures included:

• Removing or modifying components that enabled strategic use
• Recording the change in treaty notifications
• Allowing inspections or technical verification

Such measures made force reductions more durable while preserving a controlled path for modernization. Specific conversion rules differed between START I, proposed START II arrangements, and New START.

The Future of Arms Control for Ballistic Missiles After New START

After New START expired in February 2026, the United States and Russia no longer share legally binding limits on deployed strategic ballistic missiles and warheads. Existing force levels, stockpiles, and modernization programs therefore face less formal constraint than under the treaty.

Future negotiations may need to address systems that earlier agreements treated incompletely, including maneuverable reentry vehicles, hypersonic glide vehicles, and novel delivery platforms. Verification will also require updated inspections, notifications, telemetry arrangements, and data exchanges that protect sensitive information.

China’s expanding nuclear arsenal adds a wider strategic challenge. A durable framework may require participation by more than Washington and Moscow, although differences in force size, doctrine, and transparency could make a multilateral agreement difficult to achieve.

Until new limits emerge, confidence-building measures could reduce risks involving ballistic missiles. Notifications of missile tests, communication channels, and reciprocal information-sharing could help prevent miscalculation while negotiations concerning future strategic arms-control arrangements continue.