The Shield and the Sword: The Impact of Ballistic Missile Defence on Missile Proliferation
HCOC RESEARCH PAPERS NO. 15
In Israel and in Ukraine, major ballistic missile attacks have led to the large-scale use of missile defence, demonstrating its strengths and limitations in protecting military assets and populations from the effects of missile strikes.
This massive use of missile strikes on the ground, on the one hand, and the deterioration of strategic relations between major powers, on the other, are leading to a renewed interest in the acquisition of missile defence. The Trump administration has very visibly expressed this interest with the launch of the ‘Golden Dome’ programme. These investments are largely justified by the dissemination of missile technologies worldwide. Some of their promoters have asserted that they may bring stability or even contribute to curbing missile proliferation, as countries may refrain from developing weapons perceived as too vulnerable to defence. However, the spread and increased capacity of missile defence is also playing a role in missile proliferation. Indeed, countries operating missile forces are incentivised to increase their arsenals in the hopes of overcoming defensive architectures. Missiles are also becoming more sophisticated to avoid interception. Finally, the development of missile defence is leading to a negative spiral regarding the militarisation of space.
Arms control may be used to mitigate these dynamics, but it faces many challenges. Non-proliferation tools can be useful but limited, as many of the countries fielding missiles today are also involved in producing them. Confidence-building measures may play a role in restricting destabilising behaviours in space and limiting misunderstandings linked to the deployment of missile defence assets.
November 2025
Stéphane Delory & Emmanuelle Maitre
INTRODUCTION
“Missile defence has been criticised for having a potential negative impact on strategic stability and fuelling an arms race. As it is primarily developed in order to respond to the spread of missiles worldwide, it is essential to understand how defensive capacities affect proliferation dynamics.”
The emergence of nuclear intermediate-range (IRBM) and then intercontinental ballistic missile (ICBM) programmes in the 1950s very quickly led Soviet and American engineers to consider developing anti-missile systems.
As early as 1953, the development of an anti-ballistic capability was identified as a national priority by the Central Committee of the Communist Party of the Soviet Union. Progress was fairly rapid and led, in 1961, to the first successful interception of a medium-range ballistic missile (MRBM) by the experimental V-1000 interceptor. In the United States, programmes such as the Nike Zeus led to around a dozen tests in 1962–1963 but were eventually largely curbed by the Johnson administration. At the time, missile defence’s drawbacks were seen as trumping its benefits: though interception with conventional explosives was in theory possible, technical constraints implied the use of nuclear devices. Even in this case, territorial defence remained ineffective without the development of a massive and costly architecture of radars and the multiplication of launch sites across the country, raising the costs to such levels that point defence of strategic infrastructures was rapidly preferred, in the United States as well as the Soviet Union.
Therefore, freezing the offensive arsenal and tightly restricting missile defence via legally binding agreements appeared as the most effective solutions. In the Soviet Union, whose defence budget was already overburdened by massive investments in order to catch up with the United States’ offensive component, the conclusion was more or less the same. The decision was made to deploy a rudimentary defence around Moscow, but the leadership realised that expanding it would be economically unfeasible. In the framework of the first agreement on arms control (SALT I), Washington and Moscow agreed on limiting missile defence through the 1972 Anti-Ballistic Missile (ABM) Treaty.
However, the appeal of protecting the population, and not just avenging it through second strike, led to new projects, most famously Ronald Reagan’s Strategic Defense Initiative (SDI), a project that seemed to lose its relevance with the end of the Cold War but which remained influential in US thinking.
With the first Gulf War, the SDI, scaled down and re-baptised Global Protection against Limited Strikes (GPALS), appeared as the ultimate solution against emerging intercontinental missile threats. Despite the reluctance of the Clinton administration, the proliferation of weapons of mass destruction (WMDs) and their means of delivery led to new concerns. It convinced the George W. Bush administration to withdraw from the ABM Treaty and propose renewed ambitions for different layers of missile sensors and interceptors. The ‘Golden Dome’ project announced by Donald Trump on 27 January 2025 follows this heritage, but it also encompasses the recent experience of massive operational use of defences in conflicts. Since 2022, Russia has engaged significantly in missile strikes in its war against Ukraine, and acquiring and operating adequate missile defence systems has been a key concern in Kyiv. In April 2024, October 2024, and June 2025, Iran launched waves of missile strikes against Israel in the context of their bilateral conflict. The long-standing and expanded Israeli investments in missile defence have proved effective in protecting the territory against such attacks.
These precedents have fuelled an interest in missile defence, symbolised by Golden Dome, but not limited to the United States or strategic missile defence. More than 30 countries currently hold missile defence assets, the majority of which can be considered an extension of air defence aimed at tactical threats. Many other countries have displayed their interest in acquiring systems in the future, in particular in Europe through the European Sky Shield Initiative (ESSI) launched by Germany.
Missile defence has been criticised for having a potential negative impact on strategic stability and fuelling an arms race. As it is primarily developed in order to respond to the spread of missiles worldwide, it is essential to understand how defensive capacities affect proliferation dynamics.
Depending on the expectations one may have regarding the performance of missile defence, the immediate conclusions may differ. Thus, if one is fully confident that interception can be successful in almost all cases, this may be seen as decreasing the incentive to develop missiles as a category of weapons, as they become largely ineffective. However, if one believes that, through number or sophistication, it is possible to defeat defensive systems, this may be seen as fuelling a trend whereby actors expand their missile forces and increase their penetrability.
This paper explores the interactions between missile defence and offensive missile proliferation, focusing first of all on the way in which the spread of missiles has justified the development and acquisition of missile defence in order to preserve strategic stability, to respond to WMD proliferation, or for use in combat. It studies the various dynamics observed following the deployment of defensive architectures, in terms of arms racing, the modernisation and diversification of arsenals, and the militarisation of space.
Finally, it concludes on the ways in which arms control, non-proliferation, and confidence-building measures could address and mitigate these phenomena despite numerous challenges.
