Along with spring, peace, improbably, is finally in the air. While it's premature to start handing out Nobels for what's happening on the Korean peninsula, the sudden change of tone does warrant a bit of astonishment along with skepticism. There have been many numerous false dawns before now. But might this time be different?

It might. Conflicts like Korea's can stay frozen for decades, but that doesn't mean nothing is changing. As with plate tectonics, a great deal may be going on below the surface that isn't visible, such that when change happens, it can happen very suddenly. But why should that change be happening right now? With relatively new leaders in Washington and Seoul, and a very young leader in Pyongyang, it's tempting to fall back on a "great man" explanation — and to disputes about who the great man might be.

In Donald Trump's corner are those who say the president found the perfect combination of stick and carrot. He threatened "fire and fury," but also made clear that he was open to face-to-face talks leading to a peace treaty. Trump's threats seemed credible precisely because of his impetuosity, but his lack of concern for democracy or human rights gave his peace overtures just as much legitimacy.

The case for North Korea's Kim Jong Un is at least as strong. While North Korea has made (and violated) many deals before, never before have they engaged in this kind of public diplomacy, nor taken the risk of raising hopes back home the way Kim has. Kim's youth and personality, and his distance from the origins of the Korean conflict, may have made him open to taking diplomatic risks that his father never could. And it is precisely his personal exposure that has made his overtures seem more credible.

Last but hardly least, South Korea's President Moon Jae-in has perhaps the best case to make. Elected with a clear mandate to pursue reconciliation on the peninsula, Moon nonetheless began his term with a far firmer line toward Pyongyang than most anticipated, thereby winning a greater share of confidence both from his domestic opponents and from his skeptical American allies. He has deftly flattered President Trump, giving him the credit for making peace possible, and has ably managed relations with Beijing and Tokyo so as to keep a maximally free hand for himself.

If peace does come to the Korean peninsula, I doubt anyone will object too much if all the participants get prizes. But there's a "just so" quality to all such claims of personal peacemaking. Surely the end of the Cold War and the death of Kim Il Sung provided at least as good opportunities for peace. And consider Trump's predecessor. President Obama was able to negotiate a nuclear deal with Iran, restore full relations with Cuba, and complete the process of reconciliation with Vietnam by ending America's arms embargo on that former adversary. Why should North Korea specifically have eluded him, particularly when the North Korean regime did ink arms-control deals with both the Bush and Clinton administrations?

Well, consider the interests and objectives at play in each case. In Cuba, America gained nothing from maintaining a hostile posture, while reconciliation would remove one persistent irritant from hemispheric relations. The only thing any administration had to lose was the face: Making peace with Havana would effectively be admitting that American hostility had been pointless for at least 20 years. After being re-elected in 2012, Obama could be more concerned with his legacy than with political considerations, and negotiations, once commenced, proceeded rapidly to conclusion.

Reconciliation with Vietnam, meanwhile, began under the Clinton administration, and further progress under both the Bush and Obama administrations was underwritten by a strong confluence of national interests. Obama's "pivot" to Asia may be deemed a partial success or a huge mistake, but better relations with Vietnam were surely one of the most obvious moves and easiest lifts as part of an overall strategy aimed at containing Chinese military power.

The Iran nuclear deal provides perhaps the best point of comparison for any possible peace on Korea, especially since that deal was frequently attacked precisely for being too similar to previous nuclear deals with Korea. But the comparison also explains why the Obama administration was in a poor position to achieve any kind of breakthrough.

In both cases, America was dealing with a regime it viewed as unreliable and ideologically hostile, and in both cases America was prepared to grant that regime greater legitimacy in exchange for real and verifiable arms limitations. Moreover, in both cases a deal would properly be understood as at least a partial retreat by the United States. That's why the Iran deal was so vociferously opposed by America's regional allies, Israel and Saudi Arabia, who favored American military action against Iran. But it's also why a possible deal on the peninsula is being hailed in Seoul — because South Korea has far more to lose from war with the North than America does.

But that calculation may be changing, because the quality of North Korean deterrence has been improving steadily since its nuclear program began in the 1990s. And that change in turn may partly explain why the tectonic plates have finally shifted. North Korea has long held a conventional deterrent to any attack in the form of massed artillery pieces aimed at Seoul. Its nuclear and missile capabilities put Japan in range. Now their rapidly-advancing ICBM program puts them in a position to threaten retaliation against North American targets in the event of war.

Those enhanced capabilities are the stated reason for the escalating threats aimed at North Korea — but they are also the reason why America might be keen to extract itself from a situation where it is exposed to that kind of danger. The more we have to lose from war, the less eager we are going to be to start one. Moreover, North Korea knows this, and is therefore in a position to call America's bluff if America resorts once more to threats of coercion. Don't be too surprised if, when all is said and done, North Korea doesn't just get a peace treaty, but gets to keep their nuclear capability as well.

And then there's China. True peace and reconciliation on the Korean peninsula is very hard to imagine so long as American troops garrison the South, because the entire utility of North Korea to its Chinese sponsors is as a buffer state between it and the Americans. But any deal that involved a real distancing between America and South Korea would clearly be a "win" for China and a "loss" for a strategy of containment. Obama couldn't make progress on Korea, then, because his whole strategy for the Western Pacific was oriented in such a way as to bring further pressure on exactly the point of greatest resistance in that conflict.

So if peace really is in the air, it's likely less a sign of Trump's strength than of America's weakness. Graham Allison, who literally wrote the book on how hard it will be to avoid catastrophic war between America and China, calls a deal that would leave North Korea's nuclear program in place, relieve their economic isolation, and merely freeze their missile program a "big win" for America, which only makes sense if you see America's existing network of commitments as liabilities. If Trump were too eager for a bad deal, he'd see institutional pushback, from our own military and from our regional allies.

If all players treat just about any deal as a miraculous delivery from catastrophe, then clearly we were the problem all along. And if Trump has played an important role, it's in sharpening those other players' sense that the time has finally come for spring cleaning.