WASHINGTON — The number of warheads has decreased over the past year, even as countries continue to modernize their nuclear forces, according to an annual assessment of global nuclear arms.

The Stockholm International Peace Research Institute released the SIPRI Yearbook 2019 on the current state of armaments, disarmament and international security.

The report found that 13,865 warheads in existence at the start of 2019 were owned by nine nations: the United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel and North Korea.

The year before hosted an arsenal of 14,465 warheads.

“A key finding is that despite an overall decrease in the number of nuclear warheads in 2018, all nuclear weapon-possessing states continue to modernize their nuclear arsenals,” Jan Eliasson, SIPRI Governing Board chair ambassador and former deputy secretary-general of the United Nations, said in a news release.

The U.S. and Russia were the only nations that decreased their warhead inventory, by 265 and 350 respectively, according to the report.

The U.K., China, Pakistan, North Korea and possibly Israel all increased their number of warheads, SIPRI found. India and France saw no changes to the size of their arsenals.

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One big cause of the decrease in arsenal size, according to SIPRI, is the implementation of the New START Treaty between the U.S. and Russia, meant to reduce and set limits on ballistic missiles. The two nations produce more than 90 percent of the world’s nuclear arms.

The U.S. and Russia announced in 2018 that they had met the limits of the New START Treaty. But if an extension is not implemented, the treaty will expire in 2021.

What’s the United States up to?

The U.S. is in the process of modernizing its nuclear arsenal per the Trump administration 2018 Nuclear Posture Review, which put forth measures to continue a modernization program started by the Obama administration. However, the NPR moves away from reducing nuclear weapons and instead sets a plan to develop new versions while and modifying others.

The U.S. hopes to achieve its goals by expanding nuclear options to include low-yield nuclear weapons, which will expand capabilities associated with submarine-launched ballistic missiles. This would add to a U.S. arsenal that already contains 1,000 gravity bombs and air-launched cruise missiles with low-yield warhead options, according to the SIPRI report.

The NPR claims these new capabilities are necessary without evidence that the existing arsenal is insufficient.

The SIPRI report notes that America’s focus on its nonstrategic nuclear arsenal could push other nations in that same direction.

Where does Russia stand?

“Russia’s decisions about the size and composition of its non-strategic nuclear arsenal appear to be driven by the USA’s superiority in conventional forces and not by the US non-strategic nuclear arsenal or by weapons yield," according to the SIPRI report.

"Instead, pursuit of a new [submarine-launched cruise missile] to ‘provide a needed non-strategic regional presence’ in Europe and Asia could — especially when combined with the parallel expansion of US long-range conventional strike capabilities — strengthen Russia’s reliance on non-strategic nuclear weapons and potentially could even trigger Chinese interest in developing such a capability,” the report adds.

SIPRI data shows Russia has about 4,330 nuclear warheads; approximately 1,830 of them are categorized as nonstrategic.

In 2018, Russia continued long-range operations over the Arctic, Atlantic and Pacific oceans. And in December, it also sent to Venezuela two Tu-160 planes, which are part of its long-range aviation command fleet.

Russia also fired air-launched cruise missiles from a Tu-160 bomber over northern Russia in November, which caught attention because the number of cruise missiles launched.

Meanwhile, in China, India and Pakistan ...

China has an estimated 290 nuclear warheads. Though China is working to expand its nuclear forces, the report notes, it has said it’s committed to a no-first-use policy. However, the report added that China has taken steps to improve its retaliation response.

Rivals India and Pakistan each provide little information about the size of their nuclear arsenals. However, they have made separate statements about missile tests. India has an estimated 130-140 warheads, and Pakistan has an estimated 150-160 warheads.

Both nations are estimated to have increased their arsenal by 10 to 20 warheads in the last year.

North Korea has provided little transparency about it nuclear weapons capabilities, besides announcing missile tests afterward. It’s estimated the country has 20-30 warheads, which would be an increase of 10-20 warheads from a 2018 estimate.

The SIPRI report cites a lack of transparency from most nations in regard to nuclear stockpiles.