The odd couple
If there is an upside to nuclear weapons it is extended deterrence. This term refers to the "nuclear umbrella" that the United States promises to extend over its closest allies in Asia and Europe to protect against hostile nuclear powers who otherwise might be tempted to act coercively against them. Although extended deterrence is most often associated with NATO, it is also a critical feature of the American hub-and-spoke alliance system in Asia.
Confidence in U.S. extended deterrence guarantees is part of the glue that holds these alliances together. It is also an essential requirement for preventing nuclear proliferation by reassuring U.S. allies that they do not need their own nuclear arsenals. This key role that extended deterrence plays in underwriting nuclear nonproliferation is too often under-appreciated.
Given the vital role that extended deterrence plays in preserving the stability of the Indo-Pacific region - by bolstering U.S. alliances and warding off further nuclear proliferation and the very real associated risk of a fullblown regional nuclear arms race - it is worrisome that allied confidence in the American nuclear umbrella is fraying badly. This is the result of a one-two punch over the past decade that was delivered by the unlikely tagteam of presidents Barack Obama and Donald Trump. President Obama was a big fan of alliances, but famously not so much of nuclear weapons. Conversely, President Trump was a big fan of nuclear weapons, but famously not so much of alliances. Each acted on these impulses in ways that have seriously undercut extended deterrence.
Despite misgivings by allies such as Japan, President Obama effectively zeroed out American nuclear warfighting capabilities in Asia by retiring the nuclear version of the sea-based Tomahawk cruise missile. The nuclear umbrella over Asia, therefore, now relies solely on intercontinental-range strategic nuclear forces that are intended primarily to deter a nuclear attack against the American homeland. President Obama also openly flirted with a nofirst-use declaration, meaning the United States would unilaterally promise never to use nuclear weapons except in response to a nuclear attack against itself or its allies.
This, in theory, would have withdrawn nuclear weapons as a deterrent against conventional attacks up to and including the full-scale invasion of an ally. Although President Obama backed off, in part due to allies' concerns, seeds of doubt were planted about the reliability of America's extended deterrent capabilities and commitments. These doubts have been felt more acutely in Asia than Europe because NATO has other members (Britain and France) providing nuclear deterrence, and the United States continues to deploy tactical nuclear weapons there. Indeed, Washington is now upgrading these tactical nuclear weapons as a tangible signal of its enduring extended deterrence commitments to NATO.
The arrival of the Trump administration brought an attempt to restore nuclear credibility, putting no-first-use to rest and seeking to rebuild U.S. tactical and theater nuclear warfighting capabilities, including developing a new sea-based nuclear cruise missile. However, President Trump differently unnerved allies by harshly questioning the value of American alliances and repeatedly hinting that the United States might not be there if push ever came to shove, treaty obligations notwithstanding. The Biden administration is working to reassure shaken allies, but Trump's alliance-bashing has planted new seeds of doubt, this time about the reliability of America's alliance commitments writ large.