A policy with a long history
Targeting nuclear scientists began during World War II when Allied and Soviet forces raced to capture
Nazi scientists, degrade Adolf Hitler’s ability to build a nuclear bomb
and use their expertise to advance the U.S. and Soviet nuclear
programs.
In our data set, we classified “targeting” as cases in which
scientists were captured, threatened, injured or killed as nations tried
to prevent adversaries from acquiring weapons of mass destruction. Over
time, at least four countries have targeted scientists working on nine
national nuclear programs.
The United States and Israel have allegedly carried out the most
attacks on nuclear scientists. But the United Kingdom and Soviet Union
have also been behind such attacks.
Meanwhile, scientists working for the Egyptian, Iranian and Iraqi
nuclear programs have been the most frequent targets since 1950. Since
2007 and prior to the current Israeli operation, 10 scientists involved
in the Iranian nuclear program were killed in attacks. Other countries’
nationals have also been targeted: In 1980, Mossad, Israel’s
intelligence service, allegedly bombed Italian engineer Mario Fiorelli’s
home and his firm, SNIA Techint, as a warning to Europeans involved in the Iraqi nuclear project.
Given this history, the fact that Israel attacked Iran’s nuclear
program is not itself surprising. Indeed, it has been a strategic goal
of successive Israeli prime ministers to prevent Iran from acquiring
nuclear weapons, and experts had been warning
of the increased likelihood of an Israeli military operation since
mid-2024, due to regional dynamics and Iranian nuclear development.
The wrecked cars in which four of
Iran’s nuclear scientists were assassinated in recent years are
displayed on the grounds of a museum in Tehran in 2014.
Scott Peterson/Getty Images
By then, the balance of power in the Middle East had changed
dramatically. Israel systematically degraded the leadership and
infrastructure of Iranian proxies Hamas and Hezbollah. It later destroyed Iranian air defenses around Tehran and near key nuclear installations. The subsequent fall of Syria’s Assad regime cost Tehran another long-standing ally. Together, these developments have significantly weakened Iran, leaving it vulnerable to external attack and stripped of its once-feared proxy network, which had been expected to retaliate on its behalf in the event of hostilities.
With its proxy “axis of resistance” defanged and conventional
military capacity degraded, Iranian leadership may have thought that
expanding its enrichment capability was its best bet going forward.
And in the months leading up to Israel’s recent attack, Iran expanded its nuclear production capacity, moving beyond 60% uranium enrichment, a technical step just short of weapons-grade material. During Donald Trump’s first term, the president withdrew the U.S. from a multilateral nonproliferation agreement aimed at curbing Iran’s nuclear program. After being reelected, Trump appeared to change tack
by pursuing new diplomacy with Iran, but those talks have so far failed
to deliver an agreement – and may be put on hold for the foreseeable
future amid the war.
Most recently, the International Atomic Energy Agency board of governors declared Iran in non-compliance with its nuclear-nonproliferation obligations. In response, Iran announced it was further expanding its enrichment capacity by adding advanced centrifuge technology and a third enrichment site.
Even if the international community anticipated the broader attack on
Iran, characteristics of the targeting itself are surprising.
Historically, states have covertly targeted individual scientists. But
the recent multiple-scientist attack occurred openly, with Israel taking
responsibility, publicly indicating the attacks’ purpose. Further,
while it is not new for a country to use multiple counter-proliferation
tools against an adversary over time, that Israel is using both preventive military force against infrastructure and targeting scientists at once is atypical.
Additionally, such attacks against scientists are historically lower
tech and low cost, with death or injury stemming from gunmen, car bombs
or accidents. In fact, Abbasi – who was killed in the most recent
attacks – survived a 2010 car bombing in Tehran. There are outliers, however, including the Fakhrizadeh assassination, which featured a remotely operated machine gun smuggled into Iranian territory.
Israel’s logic in going after scientists
Why target nuclear scientists?
In foreign policy, there are numerous tools available if one state
aims to prevent another state from acquiring nuclear weapons. Alongside
targeting scientists, there are sanctions, diplomacy, cyberattacks and military force.
Targeting scientists may remove critical scientific expertise and
impose costs that increase the difficulty of building nuclear weapons.
Proponents argue that targeting these experts may undermine a state’s
efforts, deter it from continuing nuclear developments and signal to
others the perils of supporting nuclear proliferation.
Countries that target scientists therefore believe that doing so is
an effective way to degrade an adversary’s nuclear program. Indeed, the
Israel Defense Forces described the most recent attacks as “a significant blow to the regime’s ability to acquire weapons of mass destruction.”
Posters featuring images of Iranian nuclear scientists are displayed in Tehran, Iran, on June 14, 2025.
Fatemeh Bahrami/Anadolu via Getty Images
Despite Israel’s focus on scientists as sources of critical knowledge, there may be thousands more working inside Iran, calling into question the efficacy of targeting them. Further, there are legal, ethical and moral concerns over targeting scientists.
Moreover, it is a risky option that may fail to disrupt an enemy
nuclear program while sparking public outrage and calls for retaliation.
This is especially the case if scientists, often regarded as civilians,
are elevated as martyrs.
Targeting campaigns may, as a result, reinforce domestic support for a
government, which could then redouble efforts toward nuclear
development.
Regardless of whether targeting scientists is an effective
counter-proliferation tool, it has been around since the start of the
nuclear age – and will likely persist as part of the foreign policy
toolkit for states aiming to prevent proliferation. In the case of the
current Israeli conflict with Iran and its targeting of nuclear
scientists, we expect the tactic to continue for the duration of the war
and beyond.