Today is a good day to look back on one of Hillary Clinton’s favorite Trump quips, fittingly preserved on Twitter:

By the end of the presidential campaign, Trump had had enough of this critique; at a debate, he told Clinton the line was “starting to get a little bit old.” But controversy over Trump’s military maturity may be renewed after the president-elect tweeted a call to expand US nuclear capabilities.

As with so many of Trump’s short-form statements, it’s not clear what he means by “until the world comes to its sense regarding nukes”—we’ve asked his press team, and will update with any reply. Trump has never been one to advocate for disarmament and has, in fact, suggested that Japan and South Korea should get their own nukes. Neither does Trump set much store in the international agreements and negotiating bodies, like the United Nations, involved in making sure countries “come to their senses.” He has said that the “biggest problem, to me, in the world, is nuclear, and proliferation,” but ramping up America’s own nuclear supply is unlikely to discourage proliferation in countries like Iran and North Korea.

Many have pointed out that Trump’s tweet came just a few hours after Russian president Vladimir Putin promised to step up his own nuclear program. “We must strengthen the combat potential of our strategic nuclear forces—above all with missiles capable of penetrating existing and prospective nuclear defense systems,” Putin said in a speech to his Defense Ministry board (link in Russian). Putin directly referenced the US as a motivation for building on Russia’s weapons, saying that America is “actively modernizing its nuclear air bombs and keeping them in Europe….These moves create further risks for Russia, which we have to respond to.”

Much has been made of Trump and Putin’s mutual admiration society, but reacting to Russian nuclear bombast with an expansion of American nuclear capabilities is hardly the way to make the US, or the world, safer. It is, however, a great way to start an arms race—as theorized in the international relations term “Security Dilemma,” where one state builds up military forces for fear of another state, which then grows its own force in turn, and on and on until things are halted by either war (as in World War I) or a descaling agreement and economic or political collapse (as in the Cold War).

A far more prudent move would be, well, dialogue. Given Trump’s repeated calls for improved relations with Russia, now might be the perfect time to pick up that red telephone.