Donald Trump’s upset win stunned the leaders of US allies around the globe, but it hit South Korea particularly hard. On Wednesday, stock markets there plunged, and President Park Geun-hye convened an emergency meeting of her national security council to adjust to the reality that a man who’d talked about abandoning Washington’s long-standing promise to defend her country had just been elected president.

Now, just one day later, Trump has tried to put those concerns to rest by speaking directly with Park over the phone and promising to maintain the existing security alliance. "We will be steadfast and strong with respect to working with you to protect against the instability in North Korea,” Trump told the South Korean president, according to a statement from her office.

During the 10-minute phone call, Park reportedly told Trump, "I expect that [we] can strengthen and develop the alliance down the road for the shared interests in various areas," to which Trump responded by saying that he completely agreed with her.

She also raised North Korea's nuclear issue, and said that it was the "greatest threat" facing the two countries. "Given that in the past, North Korea staged provocations during the period of the government transition in the US, we need to closely cooperate in advance to thoroughly deter possible North Korean provocations and respond sternly if provoked."

Trump reportedly responded that the US will work with South Korea "until the end" for the security of both countries.

In other words, merely two days after having won the presidential contest, Trump appears to be walking away from one of the most alarming foreign policy positions he repeatedly put forward throughout his entire campaign.

During his run for the presidency, Trump said that if he were elected, he would consider no longer defending longstanding allies South Korea and Japan unless they agree to pay us a lot more money to do so. He also suggested South Korea and Japan should consider getting their own nuclear weapons.

"We are better off frankly if South Korea is going to start protecting itself,” Trump told CNN's Anderson Cooper back in March. “They have to protect themselves or they have to pay us." In a January interview on NBC’s Meet the Press, Trump said, “We have 28,000 soldiers on the line in South Korea between the madman and them," referring to North Korean dictator Kim Jong Un. "We get practically nothing compared to the cost of this.”

This obviously worried the South Koreans, but they — like most people around the world — likely assumed Trump wouldn’t actually win the election. When he did, they panicked. As South Korea's main stock index, the KOSPI, shed more than 2 percentage points and the local currency depreciated in value on Wednesday, Park convened an emergency meeting of the national security council, bringing together the country’s top civilian and military leaders to “closely monitor developing relations with the [incoming] Trump administration,” local news network TV Chosun reported.

That same day, Park also sent a congratulatory message to Trump expressing hopes for strengthened cooperation in handling North Korea-related issues and enhancing the US-South Korea alliance.

It must have been a really, really impressive message, since it took less than a day for Trump to speak to her directly in what was almost certainly a deliberately reassuring phone call — one of his first as president-elect.

It’s far too soon to know whether the call is a sign that Trump is going to be more sober and moderate in his policies once in office than he was on the campaign trail. But it’s certainly good news for South Korea.

Watch: How Trump thinks about foreign policy