WASHINGTON -- As commander in chief, Donald Trump will face politically fraught decisions about a nuclear arsenal in need of modernizing.

Among the open questions: How much modernization is enough? Can the U.S. get by with fewer of these weapons? Is it time to take some off hair-trigger alert?

Trump's transition website states he "recognizes the uniquely catastrophic threats posed by nuclear weapons and cyberattacks," adding he will modernize the nuclear arsenal "to ensure it continues to be an effective deterrent."

Beyond that, he has offered few specifics.

During the campaign, nuclear issues were discussed in sweeping terms.

Trump caused stirs by suggesting America's Asian allies no longer should be covered by the U.S. nuclear umbrella if they don't pay more for their defense -- or that they possibly should obtain their own nuclear bombs.

President Barack Obama and other critics questioned whether Trump could be counted on to avoid using nuclear weapons.

Ten former nuclear-missile launch operators wrote Trump lacks the temperament, judgment and diplomatic skill to avoid nuclear war.

The state of the nuclear arsenal rarely was addressed. To the extent it was, Trump showed faint understanding of its details.

At a debate with Republican rivals, he appeared unfamiliar with the concept of a nuclear triad, the Cold War-era combination of submarines, land-based missiles and strategic bombers for launching nuclear attacks.

"I think, for me, nuclear is just the power; the devastation is very important to me," he said.

Trump may need to get up to speed quickly on nuclear-weapons issues.

He soon will be overseeing a Pentagon where there is internal competition between big-dollar plans for modernizing conventional and nuclear weapons.

Michaela Dodge, a defense policy analyst at the Heritage Foundation, a conservative think tank, said the Trump administration will have a chance to reverse Obama nuclear policies she said are based on "wishful thinking," including his push to reduce the role of nuclear weapons in U.S. security strategy.

"The United States has neglected nuclear-weapons modernization programs since the end of the Cold War, and as components are expiring, the country must get ahead of the curve and modernize its nuclear systems," including the industrial plants and labs that support the arsenal, she wrote in a Heritage paper Wednesday.

Yet Trump's candidate for defense secretary, retired Marine Gen. James Mattis, is skeptical of the nuclear status quo.

"You should ask, 'Is it time to reduce the triad to a diad, removing the land-based missiles?'" he told the Senate Armed Services Committee in January 2015.

He recommended a review of fundamental questions to "clearly establish the role of our nuclear weapons. Do they serve solely to deter nuclear war? If so, we should say so, and the resulting clarity will help to determine the number we need."