By Alisha Haridasani

North Korea released three American detainees on Wednesday, a diplomatic victory for President Trump ahead of his planned meeting with the North Korean leader Kim Jong-un.

The three U.S. citizens, reportedly the last known Americans to be held by North Korea, were released after Secretary of State Mike Pompeo’s meeting with North Korean officials in the capital of Pyongyang.

Two of the detainees, Tony Kim and Kim Hak-song, were professors at the Pyongyang University of Science and Technology before they were arrested last year for “hostile acts” against North Korea. It is unclear what specifically they were accused of doing.

The third prisoner, Kim Dong Chul, was arrested in 2015 for allegedly spying on North Korea on behalf of the South Korean government, he told CNN in an interview in 2016. North Korean officials were on set during the interview and it is likely his statements were made under duress.

In an official statement, the White House said North Korea’s decision to release the three Americans, who “appear to be in good condition,” was a “positive gesture of goodwill.”

The release of the three men comes months after Trump and Kim were hurling nuclear threats against each other. Now the two leaders are preparing for a face-to-face summit to discuss nuclear disarmament on the Korean peninsula.

The shift in the tenor of relations can be attributed in part to Trump’s hardline approach to North Korea, said Martyn Williams, a journalist who has covered North Korea for over a decade.

Tighter sanctions squeezed North Korea’s economy and may have prompted Kim Jung-un to speed up the development of a nuclear weapon to increase his negotiating position. Otherwise, he might not ever have agreed to talk.

“No matter what the reason, I think it’s something to be applauded," Williams said.

The date and location of Trump’s meeting with Kim has been set, the president said, but he did not reveal those details.

The last American to be released by North Korea was Otto Warmbier, the 22-year-old American student who was also detained for "hostile acts." Warmbier was released almost a year ago; he had been in a coma and likely mistreated while in custody. He died after his return to the United States.

The three men who were released Wednesday were traveling home with Pompeo and are scheduled to land at Andrews Air Force Base in Maryland early Thursday.

For the full interview, click here.