WASHINGTON — The Pentagon on Monday officially kicked off its Nuclear Posture Review, or NPR, a major strategic undertaking that will set the Trump administration's nuclear policy.

The announcement confirmed that Vice Chairman of the Joint Chiefs Gen. Paul Selva and Deputy Secretary of Defense Bob Work will be in charge of the review. The NPR represents one of 11 major reviews Work is undertaking, at a time when his expected successor, Boeing executive Patrick Shanahan, is awaiting a confirmation hearing.

The start of the NPR is not a surprise, as U.S. President Donald Trump issued an executive order on Jan. 27 to create the review. But the formal start of the review means those seeking to influence the future of America's nuclear arsenal, estimated to cost at least $400 billion over the next decade, now have a time frame to state their case.

Here are the basic facts of the NPR:

What it is: The NPR is exactly as it sounds — a major look at all aspects of America's military nuclear capabilities. The last NPR was conducted in 2010 by the Obama administration, at a time when geopolitics of the world were different.  

It also will look at the technology involved, as the Pentagon is prepared to revamp the entirety of its nuclear arsenal. Over the coming decades, the Department of Defense will build new nuclear-capable submarines, bombers and intercontinental ballistic missiles, as well as the command and control structure to support their use.

The review will serve as a way for the Trump team to decide for itself if the path set forward from the Obama administration is the right one to continue, or if there are alternatives.

Who is involved:

While the review will be run by Selva and Work (and eventually his successor), the services will have input. Expect stakeholders like Frank Klotz of the National Nuclear Security Administration to also have a say.

But the big question is to what extent the State Department will be involved. Those individuals were included in the 2010 review at a high level, but given the lack of political appointees at State and the way the DoD has generally been seen as more powerful under the current White House, how much say the nonproliferation community will have in the NPR is up in the air.

Timeline:

The Pentagon has pledged to finish the NPR by the "end of the year," according to the news release, but the conclusion could come more quickly. During an April 4 hearing in front of the Senate Armed Services Committee, Gen. John Hyten, the head of U.S. Strategic Command, said the administration had set a six-month timeline for the review.

What will change and what won't:

Inherently, there are two key areas at which an NPR looks — policy and capability.

In terms of policy, the question is how the U.S. is postured to meet nuclear threats. This will likely be the area with the most change from the 2010 review because of how the world has changed through Russia’s annexation of Ukrainian territory and its subsequent modernization of nuclear capabilities, perceived Chinese aggression in the South China Sea, and increased missile testing from North Korea.

"We'll look at Russia, China, North Korea and Iran in particular to make sure we understand what those threats are. Iran is in compliance with the [Joint Comprehensive Plan of Action] right now, which is keeping that nuclear capability down, but they still have aggressive missile programs that we need to look at," Hyten said. "So we will look across that spectrum of the threat and we'll look at what Russia is doing in terms of violation of the [Intermediate-Range Nuclear Forces] Treaty. And then we'll look at military options in order to respond to what we see in the threat."

The second part is capability, and whether the plan to refurbish the nuclear triad is still the right way forward. Unlike the policy part of the review, there isn’t much expectation from nuclear experts that the NPR will divert from the agreed-upon modernization plan.

While "it's important to remember the new administration will take a look at the entire threat posture, the entire modernization plan," Hyten was quick to note, the "the secretary of defense, the Air Force leadership and the Navy leadership have all pledged support to modernizing the triad."

One potential aspect that could be weighed differently than in 2010 is the question of alternatives to nuclear power. Selva told an April 13 audience at an Air Force Association conference that it is time for the Pentagon to reevaluate the concept of prompt global strike, a conventional alternative to nuclear intercontinental ballistic missiles.

Asked whether that should be in the Pentagon, Selva said: "I don’t know if it will be, but it’s a good question. I don’t know. I’ll find out. We’re just doing the terms of reference for it now so I’ll make sure we include it, at least as a question of whether or not it should be in."

The biggest potential change, and one being watched closely by the nonproliferation community, is the new nuclear cruise missile, known as the Long Range Standoff weapon, or LRSO. The weapon is the farthest away from production of the major modernization programs and one that is heavily targeted by those who worry about the expansion of nuclear weapons.

However, Pentagon officials have remained firmly in support of the LRSO program, so even changes there are unlikely.