But there was no net increase in strategic nuclear weapons, which contradicted Trump's tweet prior to him taking office that stated that the U.S. "must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes".
In addition, the NPR stated that the USA had no intention of resuming nuclear testing to enhance the arsenal, "unless we find it necessary". If this continues, the risk that a nuclear weapon will be used for the first time in more than 70 years - deliberately or otherwise - will grow.
The nation's nuclear arsenal and triad had kept the USA safe 70 years for nuclear attack, and "We can not afford to let it become obsolete", Shanahan said.
US planners and security officials are anxious by the idea that Russian official policy reserves the right to use nuclear weapons first in a failing conventional conflict where the survival or territorial integrity of the Russia state is at stake, and by Russia's development of multiple nuclear systems with low yield.
Moscow has repeatedly stated that Russia has never planned to attack any North Atlantic Treaty Organisation member, with Russian Foreign Minister Sergei Lavrov saying that North Atlantic Treaty Organisation recognizes the fact, but uses it as a pretext to deploy more equipment and battalions next to Russian borders.
Rob Soofer, Deputy Assistant Secretary of Defense for Nuclear and Missile Defense Policy, said the introduction of new capabilities should in fact raise the threshold by making Russian Federation less likely to think it can get away with a limited nuclear attack against the United States or its allies.
It warned the regime would end if it ever launched a nuclear attack against the United States or its allies.
"We can not afford to let [the USA nuclear arsenal] become obsolete", Deputy Defense Secretary Patrick Shanahan told reporters at the Pentagon. Root also said there was no "automaticity" to what the USA would do in undefined "extreme circumstances".
North Korea was also mentioned in the review, with the USA describing it as a "clear and grave threat".
"There is no scenario in which the Kim regime could employ nuclear weapons and survive", the NPR said.
Russia says it will take "necessary measures" to ensure Russian security. The lack of communication-and the attendant lack of confidence in our ability to understand and influence Russian decision-making-makes USA policymakers rely more on worst-case planning; this, in turn, leads to the pursuit of weapons we may not have otherwise pursued and may not need.
In making the case for modernizing the triad, the NPR stated that the USA for decades led efforts at eat nuclear arms reduction worldwide and the efforts accelerated with the fall of the Soviet Union. It communicates to adversaries that the U.S.is willing to contemplate the use of the most devastating weapons it has at its disposal in response to large-scale attacks, regardless of how those attacks are conducted.
A Pentagon report for the first time has acknowledged that Russian Federation is building and developing an "undersea" nuclear torpedo.
Shannon said that nuclear terrorism remained a major threat in the 21st century and countries need to work to mitigate it.
The review recommends modifying "a small number" of existing nuclear warheads on Trident missiles carried on USA submarines to reduce the weapons' explosive power.
It adding that Russia's military doctrine allows the use of nuclear weapons only in case of aggression involving the use of weapons of mass destruction or where the existence of the nation is at stake.
"There are strong indications that our current strategy, posture and capabilities are perceived by the Russians as potentially inadequate to deter them", Weaver said.
"This review calls for the diverse set of nuclear capabilities that provides an American President flexibility to tailor the approach to deterring one or more potential adversaries in different circumstances", the NPR said.
Defense Secretary James Mattis said: "What we have is a nuclear deterrent, so keep those two words always together and then look at the efforts to push forward on nonproliferation and arms control, and you have to do that when you're in a position of persuasion not of hope". "They have added new types of nuclear capabilities to their arsenals, increased the salience of nuclear forces in their strategies and plans, and engaged in increasingly aggressive behavior, including in outer space and cyber space". US delivery platforms modernization and warhead recapitalization will cost about 6.4 percent at their peaks, or less than 1 percent of the federal budget.
This is why we must modernize all three legs of our nuclear triad as well as our stockpile of nuclear warheads.