The president is doing exactly that. Last week, the Air Force announced major new contracts for an overhaul of the American nuclear force: $1.8 billion for initial development of a highly stealthy nuclear cruise missile, and nearly $700 million to begin replacing the 40-year-old Minuteman missiles in silos across the United States.
While both programs were developed during the Obama years, the Trump administration has seized on them, with only passing nods to the debate about whether either is necessary or wise. They are the first steps in a broader remaking of the nuclear arsenal — and the bombers, submarines and missiles that deliver the weapons — that the government estimated during Mr. Obama’s tenure would ultimately cost $1 trillion or more.
Even as his administration nurtured the programs, Mr. Obama argued that by making nuclear weapons safer and more reliable, their numbers could be reduced, setting the world on a path to one day eliminating them. Some of Mr. Obama’s national security aides, believing that Hillary Clinton would win the presidential election, expected deep cutbacks in the $1 trillion plan.
Mr. Trump has not spoken of any such reduction, in the number of weapons or the scope of the overhaul, and his warning to North Korea a few weeks ago that he would meet any challenge with “fire and fury” suggested that he may not subscribe to the view of most past presidents that the United States would never use such weapons in a first strike.
“We’re at a dead end for arms control,” said Gary Samore, who was a top nuclear adviser to Mr. Obama.
While Mr. Trump is moving full speed ahead on the nuclear overhaul — even before a review of American nuclear strategy, due at the end of the year, is completed — critics are warning of the risk of a new arms race and billions of dollars squandered.
The critics of the cruise missile, led by a former defense secretary, William J. Perry, have argued that the new weapon will be so accurate and so stealthy that it will be destabilizing, forcing the Russians and the Chinese to accelerate their own programs. And the rebuilding of the ground-based missile fleet essentially commits the United States to keeping the most vulnerable leg of its “nuclear triad” — a mix of submarine-launched, bomber-launched and ground-launched weapons. Some arms control experts have argued that the ground force should be eliminated.
Defense Secretary Jim Mattis told Congress in June that he was open to reconsidering the need for both systems. But in remarks to sailors in Washington State almost three weeks ago, he hinted at where a nuclear review was going to come out.
“I think we’re going to keep all three legs of the deterrent,” he told the sailors.
The contracts, and Mr. Mattis’s hints about the ultimate nuclear strategy, suggest that Mr. Obama’s agreement in 2010 to spend $80 billion to “modernize” the nuclear arsenal — the price he paid for getting the Senate to ratify the New Start arms control agreement with Russia — will have paved the way for expansions of the nuclear arsenal under Mr. Trump.
“It’s been clear for years now that the Russians are only willing to reduce numbers if we put limits on missile defense, and with the North Korean threat, we can’t do that,” said Mr. Samore, who is now at Harvard’s Belfer Center for Science and International Affairs. “I think we are pretty much doomed to modernize the triad.”
At issue in the debate over the cruise missile and the rebuilding of the land-based fleet is an argument over nuclear deterrence — the kind of debate that gripped American national security experts in the 1950s and ’60s, and again during the Reagan era.
Cruise missiles are low-flying weapons with stubby wings. Dropped from a bomber, they hug the ground to avoid enemy radars and air defenses. Their computerized brains compare internal maps of the terrain with what their sensors report.
The Air Force’s issuing last week of the contract for the advanced nuclear-tipped missile — to Lockheed Martin and Raytheon Missile Systems — starts a 12-year effort to replace an older model. The updated weapon is to eventually fly on a yet-undeveloped new nuclear bomber.
The plan is to produce 1,000 of the new missiles, which are stealthier and more precise than the ones they will replace, and to place revitalized nuclear warheads on half of them. The other half would be kept for flight tests and for spares. The total cost of the program is estimated to be $25 billion.
“This weapon will modernize the air-based leg of the nuclear triad,” the Air Force secretary, Heather Wilson, said in a statement. “Deterrence works if our adversaries know that we can hold at risk things they value. This weapon will enhance our ability to do so.”
The most vivid argument in favor of the new weapon came in testimony to the Senate from Franklin C. Miller, a longtime Pentagon official who helped design President George W. Bush’s nuclear strategy and is a consultant at the Pentagon under Mr. Mattis. The new weapon, he said last summer, would extend the life of America’s aging fleet of B-52 and B-2 bombers, as Russian and Chinese “air defenses evolve to a point where” the planes are “are unable to penetrate to their targets.”
Critics argue that the cruise missile’s high precision and reduced impact on nearby civilians could tempt a future president to contemplate “limited nuclear war.” Worse, they say, is that adversaries might overreact to the launching of the cruise missiles because they come in nuclear as well as nonnuclear varieties.
Mr. Miller dismisses that fear, saying the new weapon is no more destabilizing than the one it replaces.
Some former members of the Obama administration are among the most prominent critics of the weapon, even though Mr. Obama’s Pentagon pressed for it. Andrew C. Weber, who was an assistant defense secretary and the director of the Nuclear Weapons Council, an interagency body that oversees the nation’s arsenal, argued that the weapon was unneeded, unaffordable and provocative.
He said it was “shocking” that the Trump administration was signing contracts to build these weapons before it completed its own strategic review on nuclear arms. And he called the new cruise missile “a destabilizing system designed for nuclear war fighting,” rather than for deterrence.
The other contracts the Pentagon announced last week are for replacements for the 400 aging Minuteman intercontinental ballistic missiles housed in underground silos. The winners of $677 million in contracts — Boeing and Northrop Grumman — will develop plans for a replacement force.
During Mr. Obama’s second term, the ground-based force came under withering criticism over the training of its crews — who work long, boring hours underground — and the decrepit state of the silos and weapons. Some of the systems still used eight-inch floppy disks. Internal Pentagon reports expressed worries about the vulnerability of the ground-based systems to cyberattack.
Mr. Perry, who was defense secretary under President Bill Clinton, has argued that the United States can safely phase out its land-based force, calling the missiles a costly relic of the Cold War.
But the Trump administration appears determined to hold on to the ground-based system, and to invest heavily in it. The cost of replacing the Minuteman missiles and remaking the command-and-control system is estimated at roughly $100 billion.