For decades, U.S. allies have relied on the assurance of America’s nuclear umbrella, but that comfort is quickly fading. President Donald Trump’s 2026 National Defense Strategy dropped explicit mention of extended deterrence and pressed allies to boost their own defense spending, prompting governments to rethink whether they need their own nuclear weapons, according to analysts.
The shift is raising the risk of a “proliferation cascade,” as allies perceive Washington as increasingly “disengaged and unreliable,” said Ankit Panda, senior fellow in the Nuclear Policy Program of the Carnegie Endowment for International Peace. That perception is fueling “various flavors of strategic autonomy,” he told CNBC.
Signs of retrenchment
The U.S. has taken steps that signal a narrower commitment. Trump ordered a reduction in joint military exercises with South Korea, calling them “totally inappropriate and hostile” to North Korea. Earlier last month, Washington opened talks on peaceful South Korean enrichment and reprocessing and signed a Saudi civil-nuclear pact that could potentially pave the way for domestic enrichment.
In Europe, France has moved to fill the gap. President Emmanuel Macron announced in March the country’s first warhead increase since 1992 and pledged to extend France’s nuclear umbrella to other EU nations under a “forward deterrence” partnership. Nine countries, including Germany and Greece, have joined.
Japan is also stepping up its nuclear defense posture. Prime Minister Sanae Takaichi’s reluctance to rule out revising Japan’s three non-nuclear principles has drawn scrutiny, with speculation she could shift away from the decades-old commitment to refrain from any role in deploying nuclear weapons. Leaders of Lithuania and Finland, both bordering Russia, have moved closer to scrapping bans on domestic deployment of nuclear weapons.
Risks of escalation
None of these developments yet amounts to a decision to build a bomb, but any move toward nuclear capability could backfire. “You cannot build or deploy a nuclear deterrent without immediately raising tensions and forcing adversaries to react,” said Andrew Facini, senior fellow at the Council on Strategic Risks. That could accelerate the very security risks a proliferator hopes to avoid.
Iran offers a cautionary example. Its pursuit of enriched uranium was at least partly responsible for the current Middle East war, and the Trump administration has insisted “Iran cannot be allowed to have a nuclear weapon.” While Iran is not known to possess a weapon, the U.S.-Israeli strikes in 2025 may push Tehran to go nuclear, said Alexandra Bell, president and CEO of the Bulletin of Atomic Scientists. “We don’t know if by the act of attacking them we have pushed the Iranians, fully and finally, to decide to actually go nuclear,” she said.
Arms race and treaty strain
All nine nuclear-armed states — the U.S., Russia, China, the U.K., France, India, Pakistan, North Korea, and Israel — continue to modernize and expand their arsenals. Russia and the U.S. together hold about 83% of usable nuclear warheads, according to a June report from the Stockholm International Peace Research Institute (SIPRI). “By reaching for nuclear solutions, states are creating new risks and fueling arms-race dynamics,” said Hans Kristensen, a SIPRI senior fellow, adding that the push will likely reverse decades of demobilization efforts.
Of the more than 12,000 warheads owned by nuclear powers, over 9,000 are in military stockpiles for potential use. An estimated 4,012 are deployed with missiles and aircraft, and up to 2,200 are on high alert, launchable within minutes.
The Nuclear Non-Proliferation Treaty (NPT), in force since 1970, has “by and large stemmed the flow of mass proliferation,” Bell said. But a review conference at the UN in May failed to reach consensus, and UN Secretary-General Antonio Guterres warned the treaty is “eroding.”
Bell urged Washington to reduce incentives for other states to acquire nuclear weapons. “Building things is hard. Breaking things is very easy,” she said. “If we break the NPT, we may never recover from that lapse in security.”
Source: www.cnbc.com — https://www.cnbc.com/2026/08/19/nuclear-proliferation-defense-risk-trump-umbrella-.html
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