Pyongyang claimed on Wednesday that it already has developed nuclear weapons small enough to fit on missiles. The powerful National Defense Commission declared “it is long since [North Korea’s] nuclear striking means have entered the stage of producing smaller nukes and diversifying them.” It also highlighted its ability to put miniaturized nuclear warheads on short-range, medium-range, and long-range missiles. The term “diversified” may refer to the regime possessing both plutonium-based and uranium-based nuclear weapons.

Pyongyang’s proclamation occurred shortly after its successful first underwater ejection test of a submarine-launched ballistic missile (SLBM), refocusing attention on the regime’s growing nuclear and missile threats to the United States and its Asian allies.

Though some Western media tout this as North Korea’s first such claim, Pyongyang has been making the assertion since at least its third nuclear test two years ago. In March 2013, Kim Jong-un declared, “The United States is now most fearful of our miniaturized, reduced-weight, and diversified nuclear deterrent.” The Korea People’s Army Supreme Command also bragged of its “lighter and smaller nuclear weapons [able to] attack the US with diversified precision nuclear strikes.”

In recent years, U.S. and South Korean officials have increasingly concluded that North Korea has achieved warhead miniaturization. This year, the four-star U.S. commanders of U.S. Forces Korea, Pacific Command, and NORAD have all publicly stated their assessment that Pyongyang possesses nuclear weapon–equipped missiles.

As The Heritage Foundation concluded in a research study last year,

[A]vailable unclassified evidence indicates North Korea has likely already achieved warhead miniaturization, the ability to place nuclear weapons on its medium-range missiles, and a preliminary ability to reach the continental United States with a missile. As such, the United States and its allies face a greater threat today than is widely construed.

Some experts, however, continue to downplay North Korea’s nuclear warhead capabilities, asserting that Pyongyang is still “several years” away. Ironically, they have been asserting this for several years. In the past, experts frequently underestimated North Korea’s nuclear and missile programs due to ideologically driven analysis, political expediency, and the belief that a technologically and economically backward nation could not achieve the necessary breakthroughs.

Skeptics initially dismissed evidence of North Korea’s plutonium-based nuclear weapons, highly enriched uranium program, involvement in constructing a Syrian nuclear reactor, and ability to develop long-range missiles. U.S. intelligence estimates of these programs were dismissed as politically motivated, until they were proven indisputably correct. North Korea’s latest nuclear claims generated analytic debate over whether the SLBM had been from a submarine or a submerged test barge, missing the more important point that the test confirmed Pyongyang’s intent to expand its nuclear arsenal with new threat capabilities.

Recent U.S. expert studies assess a higher North Korean arsenal than previously predicted. Dr. Siegfried Hecker, former Director of the Los Alamos Nuclear Laboratory, concluded that North Korea could have 20 nuclear weapons by 2016. The Korea Institute at Johns Hopkins School of Advanced International Studies (SAIS) predicted a worst-case scenario of Pyongyang having 100 nuclear weapons by 2020.

Given Pyongyang’s repeated rejections of U.S., South Korean, Japanese, Chinese, and Russian attempts at engagement, Washington and its allies should take the necessary steps to defend themselves against the growing North Korean nuclear threat, such as deploying the Terminal High-Altitude Area Defense missile defense system to South Korea.