Nukes all around? A fraying U.S. nuclear umbrella is pushing allies to weigh defense options, raising risk of a proliferation cascade

A woman rolls a baby stroller past a replica of the Soviet RDS-4 nuclear bomb installed in memory of its creators in a park in Moscow on July 29, 2026. Alexander Nemenov | Afp | Getty ImagesFor decades, allies worldwide rested in the comfort of the U.S. nuclear umbrella, confident they didn't need their own weapons of mass destruction.That belief is rapidly evaporating as President Donald Trump's latest National Defense Strategy for 2026 dropped any explicit mention of extended deterrence and has pressed allies to spend more of their own money on defenses.The change is prompting more governments to reconsider whether to acquire nuclear weapons of their own, raising the risk of a proliferation cascade, analysts say. Allies almost universally perceive Washington as becoming more "disengaged and unreliable," prompting "various flavors of strategic autonomy," said Ankit Panda, senior fellow in the Nuclear Policy Program of the Carnegie Endowment for International Peace. Most recently, U.S. President Donald Trump ordered a reduction in joint military exercises with ally South Korea, saying that the exercises sent a signal that was "totally inappropriate and hostile" to North Korea. Earl...