After years of diplomatic wrangling, months of preparation, and weeks of uncertainty, President Donald Trump met North Korean leader Kim Jong Un in a landmark summit in Singapore on Tuesday.

Moments after shaking Kim's hand, Trump said “we will have a terrific relationship.”

“I feel really great,” Trump said alongside Kim. “We're going to have a great discussion.”

Kim apparently echoed the sentiment: “It was not easy to get here … the old prejudices and practices worked as obstacles on our way forward, but we overcame all of them and we are here today,” Kim said through his interpreter.

Trump, Kim Meet For The First Time In Historic North Korea Summit

U.S. President Donald Trump shakes hands with North Korea leader Kim Jong Un at the Capella resort on Sentosa Island Tuesday, June 12, 2018 in Singapore.Associated Press/Evan Vucci

Hours before meeting Kim, Trump railed against naysayers who criticized his decision to entertain Kim on an international stage. Kim's regime has been condemned by human-rights groups and security experts for numerous violations over the years.

“The fact that I am having a meeting is a major loss for the U.S., say the haters & losers,” Trump said in a tweet. “We have our hostages, testing, research and all missile launches have stopped, and these pundits, who have called me wrong from the beginning, have nothing else they can say! We will be fine!”

Despite this being the first time a sitting U.S. president met with a North Korean leader, some foreign-policy experts expressed doubt about the meeting and theorized it would give Kim and his regime the global diplomatic legitimacy it has long craved.

The U.S., as part of a longstanding posture of isolating the North, has previously rejected the notion of meeting with that country's leader.

Former U.S. officials have also thrown cold water on the summit, which they say was hastily arranged. Summits typically are not held until after extensive backchannel negotiations between lower level officials. Trump's approach, however, has turned the typical diplomatic norms upside down, which has rankled some policy experts.

“This is what happens when you jump too early to a summit,” Victor Cha, the former director for Asian affairs for the National Security Council and the former nominee for U.S. ambassador of South Korea, told The Washington Post in May. “If this breakdown means North Korea is no longer beholden to their missile-testing moratorium, that takes us to a very bad place.”

The dramatic first season on the Korean Peninsula

The meeting between Kim and Trump is a stark shift from the fierce rhetoric the two leaders traded in 2017.

Last year, Pyongyang conducted a bevy of nuclear and missile tests that experts said was an indication the regime was in the advanced stages of development. In 2017, the regime reportedly launched 23 missiles, including its first intercontinental missile capable of reaching the U.S. mainland.

Analysis compiled by the U.S. Defense Intelligence Agency and reported by The Washington Post in August made that threat even more real, finding that Pyongyang had successfully created a miniaturized nuclear warhead that could fit on a missile. The regime then conducted its most powerful nuclear test weeks later.

However, at the start of 2018, North Korea signaled it was willing to normalize ties with South Korea and the U.S.. After Pyongyang sent a delegation to participate in the 2018 Winter Olympics in Pyeongchang, South Korea, Kim indicated that he intended to thaw the icy relations by agreeing to reestablish communication channels with the South. He met one-on-one with South Korean President Moon Jae-in in April.

“A new history starts now, an age of peace, from the starting point of history,” Kim wrote in a guest book at South Korea's part of the border village of Panmunjom.

Moon and Kim signed the Panmunjom Declaration of Peace at the inter-Korean summit, outlining broad agreements that hinted at bringing a formal end to the Korean War, and to “boldly approach a new era of national reconciliation, peace and prosperity.”

“The two leaders declare before our people of 80 million and the entire world there will be no more war on the Korean Peninsula and a new age of peace has begun,” the declaration said.

Trump: A master negotiator or the apprentice?

Trump and his officials have largely credited Kim's willingness to conduct talks to the Trump administration's “maximum pressure” campaign on North Korea. The U.S. enacted sweeping sanctions that targeted the North's imports and exports, creating an economic vice that is believed to have been felt by Kim and North Korea's elite.

Proponents of the campaign agreed that the regime was feeling the squeeze. Leading up to the summit, North Korea made several concessions, including releasing three Korean-American captives and announcing it would destroy a major nuclear test site.

“In 2017, able to get more economic pressure on the regime than it's ever felt before,” Cha said to TIME. “I was always of the view that that policy would work, because North Korea doesn't tend to lash out militarily when they feel economic pressure. They want to come to the negotiating table and see how they can get that pressure taken off.”

Much to the chagrin of international activists, the Trump administration has reportedly set aside the issue of North Korean human-rights violation ahead of the summit.

Little is known about Trump's and Kim's demands; however, the U.S. is likely to advocate for the complete, verifiable, irreversible denuclearization (CVID) of the regime, as American officials have said in the months leading up to the summit.

Kim, on the other hand, is believed to be pushing for complete, verifiable, irreversible guarantee of North Korea's security (CVIG) — a security guarantee that seeks the removal of the U.S.'s nuclear defense umbrella in South Korea.

Related: What You Need To Know About The Trump-Kim Summit In Singapore »

The two leaders have often been compared to each other due to their unpredictable shifts in policy. And North Korea's pattern of behavior in reneging on previous agreements may be factored into any demand Trump and his diplomats will make.

Regardless of the route North Korea takes during the summit and in the days afterward, Trump has signaled that even though talks between the two countries may be extended, time was of the essence.

“I feel that Kim Jong Un wants to do something great for his people, and he has that opportunity,” Trump told reporters in Singapore. “And he won't have that opportunity again. It's never going to be there again.”

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