Among the other investments planned is the so-called "low-yield" nuclear warhead that could be launched underwater. This warhead with less explosive force is in response to Russia, which developed underwater drones that are capable of carrying low-yield warheads.
"The only purpose of this adding another delivery type is to enable ... a more surgical, low-yield strike," said Gronlund, a physicist by training. "We're sort of primed to engage in this kind of nuclear warfighting. This brings us closer to the edge. We still need some kind of spark though."
Also, Gronlund said that the new nuclear warhead isn't needed because the U.S. already has bombs and air-launched cruise missiles with a low-yield capability. She also said the Trump policy is counter to the "very long glide path" of the U.S. reducing its emphasis on nuclear weapons use.
But the NPR argues that the "low-yield" warhead for the U.S. Trident missile would be "a comparatively low-cost and near-term modification to an existing capability that will help counter any mistaken perception of an exploitable 'gap' in U.S. regional deterrence capabilities."
The document also calls for the U.S. to develop "a modern nuclear-armed sea-launched cruise missile." It said the "low-yield" option on the Trident missile and the sea-launched cruise missile would "provide additional diversity in platforms, range, and survivability, and a valuable hedge against future nuclear 'break-out' scenarios."
"Unfortunately, this NPR does not argue for maintaining 'strategic stability' nor does it explain whether, how and why the call for new U.S. nuclear capabilities will reduce the threat of nuclear conflict," said Thomas Countryman, former acting undersecretary of State for arms control and the chairman of the Arms Control Association, a nonpartisan disarmament group based in Washington.
But others maintain that the new nuclear weapons strategy makes sense and argue that there's a need to strengthen nuclear deterrence capabilities, including through smaller "low-yield" bombs.
"It realistically assesses international conditions and addresses impacts of these developments for nuclear forces, including strengthening deterrence by reintroducing low-yield nuclear weapon options to the U.S. nuclear weapon arsenal," said Dodge, the Heritage analyst.
Dodge also said the document "highlights negative security trends since the end of the Cold War, particularly the mistaken belief that Russia's trajectory of development will be benign."