Faced with the daunting expense of modernizing America’s nuclear arsenal, some critics have suggested the U.S. could achieve its deterrence aims with fewer warheads, perhaps even eliminating one leg of the so-called nuclear triad that comprises land-based intercontinental ballistic missiles, submarine-launched ballistic missile, and strategic bombers.

Back in March, Rep. Adam Smith, D-Wash., the powerful chairman of the House Armed Services Committee, said he thought the U.S. could deter Russia and China even without ICBMs. After receiving harsh criticism from Republicans on Capitol Hill, Smith walked back those comments to say that he favored modernizing nuclear weapon systems but thought the U.S. could reduce the number of warheads in its arsenal.

“I think a deterrent policy, having enough nuclear weapons to ensure that nobody launches a nuclear weapon at you because you have sufficient deterrent, I think we can do that with fewer warheads,” Smith said at the Carnegie Endowment for International Peace. “I’m not sure whether that means getting rid of one leg of the triad or simply reducing the amount in each leg.”

But Air Force Chief of Staff Gen. Dave Goldfein believes that preserving the nation’s air, land and sea nuclear forces is paramount.

“When asked whether we still require all three of these legs of the triad, I answer, ‘We do,’” Goldfein said at the Mitchell Institute June 26. “And this position has been backed up by every president and Congress since the nuclear umbrella was created,” he said.

The U.S. has had a nuclear triad since the 1960s, but many of its elements are outdated.

For example, B-52 bombers from the 1950s are still in use, although they will soon be re-engined and augmented by the B-21 nuclear-capable bomber starting in the mid-2020s. The Minuteman III intercontinental ballistic missile was first installed in the 1970s and has undergone multiple life extensions, but the Air Force would prefer it didn’t undergo another.

Updating and modernizing these elements is especially critical to remain globally competitive, as Russia and China are moving swiftly to advance their own nuclear capabilities, Goldfein said. He also noted that Russia and China have not responded in kind to U.S. efforts to minimize the function of nuclear weapons in the event of war.

“I would never advise our civilian leaders to unilaterally disarm, when adversaries are building more capacity and capability, without getting anything in return,” he said. “And I would never advocate to place ourselves in a position where we might give up our second-strike capability … causing a potential change in enemy calculus.”

According to a January Congressional Budget Office analysis, it will cost $494 billion from 2019 to 2028 for the Pentagon and Department of Energy to update the nation’s nuclear arsenal.

Although Goldfein admits nuclear modernization comes with a hefty price tag, he warned that the “price of preserving our nuclear deterrent is nothing compared to the price of losing it.”

“History has shown the nation’s investment in these elements [is] well worth it, especially when compared to the costs — financial and in lives lost — of world wars that we have not experienced since 1945,” he said.

The Trump administration’s Nuclear Posture Review, released in February 2018, called for modernizing the nation’s nuclear elements.